Cribsheet: A Data Driven Guide to Better, More Relaxed Parenting, from Birth to Preschool

By Emily Oster

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Introduction

One of the great themes of your parenting life: you have way less control than you think you do.

This is a problem for learning from the data. Studies of breastfeeding show time and again that breastfeeding is associated with better outcomes for kids, better school performance, lower obesity rates, and so on. But these outcomes are also linked with a mother’s education, income, and marital status. How can we know if it is the breastfeeding or the other differences among women that causes the better school performance and lower obesity? One answer is that some of the data is better than other data. In thinking about these decisions, I used my economic training, especially the part where I try to tease causality out of data, to try to separate the good studies from the less good ones.

But the same data does not always lead everyone to the same decision. Data is an input, but so are preferences. In deciding whether to breastfeed, it is useful to know what the benefits are (if any), but it’s also crucial to think about the costs. You may hate breastfeeding; you may plan to return to work and hate pumping. These are reasons not to breastfeed. Too often we focus on the benefits at the expense of thinking about the costs.

Your choices can be right for you but also not necessarily the best choices for other people. Why? You are not other people. Your circumstances differ. Your preferences differ. In the language of economics, your constraints differ.

This book will not tell you what decisions to make for your kids. Instead, I’ll try to give you the necessary inputs and a bit of a decision framework. The data is the same for us all, but the decisions are yours alone.

The goal of this book is not to fight against any particular piece of advice but against the idea of not explaining why. Armed with the evidence and a way to think about decisions, you can make choices that are right for your family. If you’re happy with your choices, that’s the path to happier and more relaxed parenting. And, hopefully, to a bit more sleep.

PART ONE: IN THE BEGINNING

CHAPTER 1: The First Three Days

So a bath isn’t a terrible thing, but there is also really no reason to bathe your kid other than some gross out factor. Most of the blood can just kind of be wiped off. I should perhaps not admit this, but they never bathed Finn in the hospital at all, and we still waited the family standard two weeks to actually give him a bath at home.

In principle, circumcision can be done more or less as soon as you can confirm that the penis is working properly (i.e., after the first time the kid pees).

The American Academy of Pediatrics suggests the health benefits of circumcision outweigh the costs, but they note correctly that both benefits and costs are quite small. This decision will often come down to personal preference, some type of cultural linkage, or just a desire to have your son’s penis look a particular way. These are all valid reasons to do it or not do it.

If you have the option to send your kid to the nursery for a few hours and you want to do that, you shouldn’t feel shame in doing so. There is no good evidence that you’re disrupting your breastfeeding relationship, if that’s important to you. And if you find yourself falling asleep with your baby in the bed, ask for help.

The authors of this paper created a website, www.newbornweight.org, where you can enter the time of birth of your child, method of birth, method of feeding, birth weight, and current weight and learn where they are in the distribution.

A final note: The major concern about weight loss is that it is a signal of dehydration. But this is also something you can monitor directly. If your baby is peeing with some frequency and does not have a dry tongue, there’s a very good chance he’s not dehydrated. Conversely, if you see these signs, supplementation may be a good idea, even if there isn’t too much weight loss.

As there is for determining risky infant weight loss, there is also a website that will tell you if jaundice treatment is recommended given bilirubin levels: www.bilitool.org.

For premature infants, there is very good evidence that you should delay cord clamping.

On net, the recommendations increasingly favor delaying the cord cutting, if possible.

CHAPTER 2: Wait, You Want Me to Take It Home?

There are a variety of blankets that will allow you to successfully swaddle your baby so they can’t escape.

The key is that these have some way of keeping your baby tucked in other than folding, for example, many yards of fabric or some Velcro. We used one called the Miracle Blanket.

These risks arise if the baby’s legs are not able to flex at the hip, so it is crucial to swaddle the baby in a way that allows them to move their legs around.

The most important thing is to try to take care of yourself. Infant crying links to postpartum depression and anxiety, and parents, both parents, will need a break.

There are a few things that may improve colic, but since the cause of colic is poorly understood, solutions are hard to develop. Many of the theories involve digestion, poorly developed gut flora or an intolerance to milk protein. These are just theories, although, since they are the leading theories, most of the proposed solutions relate to them.

Two treatments have some known success with colic. One is supplementation with a probiotic, which a number of studies have shown to reduce crying.

The other treatment that has shown some success is managing the baby’s diet, either by changing formula types or, if the baby is breastfed, changing the mother’s diet.

One recommendation is to switch to a soy based or hydrolyzed protein formula10 (most of the major formula makers, Similac, Enfamil, have versions of these). The evidence on formula switching is mostly financed by formula companies, so do with that what you will, but it may be worth a try.

The standard recommendation is the elimination of all dairy, wheat, eggs, and nuts, so this means a pretty dramatic dietary change. Unfortunately, we don’t know if just one of these foods, all, or a combination makes the difference, and the evidence is overall pretty limited (this definitely does not work for everyone).

If you want to collect data and make pretty graphs, go for it. But remember that this is the illusion of control, not actual control.

This suggests that as your child ages, say, into toddlerhood and beyond, it is not necessarily a good idea to wipe down everything with hand sanitizer or bring your own disposable placemats to restaurants. Your kid probably shouldn’t lick the floor at the airport, as mine have occasionally done, but going a bit more in the exposure direction may be sensible.

These reasons, many doctors are reasonably lax about children’s germ exposure after infancy. But virtually all doctors will suggest you try to avoid exposure to illness in the baby’s first couple of months. One reason for this is simply that the smaller the child, the more vulnerable they are to serious complications. But a second reason is that for very young infants, especially those younger than twenty eight days, medical protocols suggest much more aggressive interventions in response to illness.

CHAPTER 3: Trust Me, Take the Mesh Underwear

There is some evidence that warm compresses on the perineum during the pushing stage of labor can prevent very severe tears.

It will also likely hurt to poop. This depends, again, on how traumatic your birth experience was. It is common to give women stool softeners to improve the first postbirth bowel movement.

Lingering Consequences: A few days later, you’re home. The most immediate consequences, heavy bleeding, uncomfortable first pee, etc., will be over. You will not, however, feel normal. First of all, you’ll still look pregnant. This appearance will subsist for a few days or weeks. Then you’ll just have a bunch of floppy skin. This does resolve eventually (by which I mean weeks or months later, not days), but it’s a little disconcerting to look down at. Even once the floppy skin is gone, many of us find we have what is referred to as “mummy tummy,” a pouchy stomach that doesn’t ever seem to quite snap back.

Once you can exercise, it can be challenging to find time in your schedule, but if it’s important to you, you should try. Exercise can help combat postpartum depression and generally improves mood. Yes, there are other demands on your time, but taking care of yourself also matters.

A final note: Sex after childbirth can be painful. Breastfeeding promotes vaginal dryness and lowers your sex drive. In addition, injuries during birth can have persistent effects. Many women, after having a small person attached to them nearly constantly, really do not want to be touched. Most women need some lubrication the first few times they have sex after giving birth to deal with vaginal dryness. And you want to take it slow at the start. And, of course, this all focuses on penetrative vaginal sex. Other activities, oral sex, either given or received, may be easier to restart, and could be more enjoyable early on.

In the first days and weeks after your baby arrives, you will experience a wave of hormones. Most women find they are emotionally sensitive during this period. This is not, for example, the time to watch the first fifteen minutes of the movie Up.

This early experience is sometimes referred to as the “baby blues” and is self limiting in the sense that the hormone surge is worst in the first few days after giving birth and dies down a couple of weeks later.

Treatment for postpartum depression proceeds in stages. For mild depression, the first line of treatment is to try to treat without drugs. There is some evidence that exercise or massage can be helpful. Or, perhaps most important, sleep. For new parents, in particular, lack of sleep can be a huge contributor to mild depression.

PART TWO: THE FIRST YEAR

CHAPTER 4: Breast is Best? Breast is Better? Breast is About the Same?

We know breast milk contains antibodies, so it is therefore more plausible that it is protective against some illnesses.

The study found two significant impacts: In the first year, breastfed babies had fewer gastrointestinal infections (i.e., diarrhea) and lower rates of eczema and other rashes.

Certainly, it seems reasonable to conclude that breastfeeding lowers infant eczema and gastrointestinal infections. For the other illness outcomes, the most compelling evidence is in favor of a small reduction in ear infections in breastfed children.

SIDS is rare; ear infections and colds are common. Your kids will get colds for sure, whether you breastfeed or not. SIDS deaths, in contrast, occur in about 1 of every 1,800 births; among babies with no other risk factors (not premature, not sleeping on their stomachs), this is perhaps 1 in 10,000.

It is certainly true that obesity and breastfeeding are correlated, as kids who are breastfed are less likely to be obese later in life. But this correlation doesn’t show causation, it doesn’t prove that those kids who go on to become obese do so because they weren’t breastfed.

One reason is that people seem to love a scary or shocking narrative. “Report: Formula Fed Children More Likely to Drop Out of High School” is a more clickable headline than “Large, Well Designed Study Shows Small Impacts of Breastfeeding on Diarrheal Diseases.” This desire for shock and awe interacts poorly with most people’s lack of statistical knowledge. There is no pressure on the media to focus on reporting the “best” studies, since people have a hard time separating the good studies from the less good ones.

First, they compare children who are breastfed with those who are not with a few simple controls. When they do this, they find large differences in child IQ between the breastfed kids and those who are not. In the second phase, they add an adjustment for the mother’s IQ, and find that the effect of breastfeeding is much smaller, much of the effect attributed to breastfeeding in the first analysis was due to differences in the mothers’ IQs, but does still persist. But then the authors do a third analysis where they compare siblings, children born to the same mother, one of whom was breastfed and one who was not. This is valuable because it takes into account all the differences between the moms, not just their performance on one IQ test. In this analysis, researchers see that breastfeeding doesn’t have a significant impact on IQ. This suggests that it is something about the mother (or the parents in general), not anything about breast milk, that is driving the breastfeeding effect in the first analysis.

In conclusion, there is no compelling evidence for smarty boobs.

For some women, breastfeeding makes them feel empowered and happy. It’s convenient to have a ready food source anywhere they go, and they find nursing their baby to be a peaceful and relaxing time. That’s great! For others, breastfeeding makes them feel like a cow. They hate lugging the breast pump around if they have to pump. It’s hard to tell if the baby even likes to nurse or is getting enough food. Their nipples hurt, and the experience basically sucks. All this is to say that many of the purported benefits of breastfeeding for moms are really subjective. I have been on both sides of this, as have most of my friends. There were definitely moments, especially with Finn, when I thought it was a superconvenient and awesome option. And then there were others, I am thinking in particular of an experience pumping in the bathroom at LaGuardia Airport, when the whole thing seemed like a farce. One of the things on every pro breastfeeding list is “saves money.” This really depends. Yes, formula is expensive, but so are nursing tops, nipple creams, nursing pads, and the fourteen different breastfeeding pillows you need to make it work. And, more important, there is your time, which is valuable.

There is one benefit that does have a larger and more robust evidence base: the link between breastfeeding and cancers, in particular breast cancer. Across a wide variety of studies and locations, there seems to be a relationship here, and a sizable one, perhaps a 20 to 30 percent reduction in the risk of breast cancer. Breast cancer is a common cancer, almost 1 in 8 women will have a form of it at some point in their lives, so this reduction is big in absolute terms. This data isn’t perfect, for one thing, the controls for maternal socioeconomic status are almost always missing, but the case for causality is bolstered by a concrete set of mechanisms. Breastfeeding changes some aspects of the cells of the breast, which makes them less susceptible to carcinogens. In addition, breastfeeding lowers estrogen production, which in turn can lower the risk of breast cancer. After all that focus on the benefits of breastfeeding for kids, it may be that the most important long term impact is actually on Mom’s health.

Short Term Baby Benefits: Fewer allergic rashes. Fewer gastrointestinal disorders. Lower risk of NEC Fewer ear infections (maybe).

“The most convincing evidence on the value of breastfeeding comes from mothers who have done it. They tell of the tremendous satisfaction they experience from knowing that they are providing their babies with something no one else can give them … from feeling their closeness.” At least for me, this resonated very strongly. I am happy I nursed my children because, aside from some of the early hot closet incidents, I enjoyed it. It made for many nice moments with them, doing something we could only do together, watching them fall asleep. This is a great reason to do it, and a good reason to try. It’s also a good reason to support women who want to try, and to not shame women who breastfeed in public. But this is not a good reason to judge yourself if you decide breastfeeding isn’t for you.

CHAPTER 5: Breastfeeding: A How To Guide

The moms who had their infants skin to skin were more likely (72 percent versus 57 percent) to be breastfeeding at six weeks; they also reported less pain while being stitched up after birth.

Despite the warnings, there is simply no evidence that the use of pacifiers impacts breastfeeding success.

Smoking during pregnancy slows down milk production, as does obesity.

Good news: mostly, breastfeeding moms have no dietary restrictions. Let’s start with the food part. The only food women are medically advised to avoid during breastfeeding is high mercury fish. That’s it! No swordfish, king mackerel, tuna. But other fish are fine, as are unpasteurized cheeses, sushi, rare steak, deli meats, and on and on. If your baby is suffering from colic, excessive crying as an infant, there is some evidence that avoiding common dietary allergens could help.

There is something of an old wives’ tale that gassy foods (cauliflower, broccoli, beans) lead to a gassy baby, and can make colic worse. I can find only one paper on this, and it is based on a mail survey that asked parents about many foods and compared the food consumption for babies with colic to those without. Although this study did claim to find some minimal evidence that cauliflower and broccoli lead to more colic, the problems with the data collection and analysis are so significant (use of mail survey with poor response rate, excessive response among people who were hyperconcerned about breastfeeding, problems with statistical precision) that I think it is safe to ignore it. Eat what you want.

What about alcohol? Many women hear, from the internet, typically not from their doctors, that they should avoid alcohol altogether, or that if they drink at all, they should “pump and dump.” On the other side, some people will tell you that having alcohol (beer, specifically) will increase your milk supply. So you should have more! Are either of these true? No, not really. When you drink, the alcohol level in your milk is about the same as your blood alcohol level. The baby consumes the milk, not the alcohol directly, so the level of alcohol they are exposed to is extremely low. One paper carefully calculates that even if you had four drinks very quickly and then breastfed at the maximum blood alcohol level, the baby would still be exposed to only a very, very low concentration of alcohol, one that is extremely unlikely to have any negative effects. And this is in a kind of “worst case scenario.”

On the flip side, I’m sorry to report that drinking does not improve your milk supply. If anything, it may lessen it a bit, so if you are struggling with supply early on, do not consider alcohol as a supply booster.

Along with alcohol, many women worry about the impact of taking medication while nursing. It’s beyond the scope of this book to go through the interactions of every medication, but generally, most are safe and your doctor is a good source for more information. You can also search for virtually any drug in the LactMed database online. Two drug groups are common enough to deserve some discussion here: painkillers (i.e., those you’d use after birth) and antidepressants. Childbirth is uncomfortable, and afterward, you’ll likely be in significant pain for a few days or longer. The first line of defense is Tylenol or ibuprofen, typically (in the latter case) in quite high doses. These are well tolerated and fine for use while breastfeeding. However, ibuprofen isn’t always enough, especially for women who have had a C section. Codeine used to be a common next step, but more recent data has suggested that exposure during breastfeeding has significant nervous system effects in babies; it makes them extremely sleepy, and in a few examples, there were thought to be severe consequences. As a result, newer recommendations generally advise against prescribing codeine or other opioids like oxycodone.

If you have been on antidepressants before and know which one is effective for you, then that is what you should use. If not, the first line SSRIs for nursing mothers are paroxetine and sertraline, which transfer to breast milk at the lowest levels. A final note is on caffeine. Most people find it’s fine to have caffeine while nursing, and there is certainly no literature suggesting risks to the baby. However, some babies are quite sensitive to caffeine and get very fussy and irritable. If you find this is the case, you may have to avoid it. Tap water, though? Go for it. Hydration is important for everyone, breastfeeding or not. Take the water anywhere you can get it.

There are basically three reasons to use a breast pump. Let’s review. First, if you are struggling with low supply early on, your doctor may suggest you try pumping after some (or all) feedings to increase your supply. As noted earlier, the theory is good here, although there isn’t much empirical evidence. If this is your only use of the pump, it may be a good idea to rent one from the hospital, it will be a better quality pump. And you probably aren’t going anywhere much at first. Second, many women pump early on so they can start to give their baby the occasional bottle. Of course, you will pump while the kid gets the bottle, but if you want to have one ready for the first time, you’ll have to pump beforehand. You may also want to do this to build up a supply of milk if you are planning to return to work. I recall the logistics of this being complicated, especially when I was nursing Penelope and my supply was underwhelming. Some of the books told you to pump two hours after a feeding, even if the baby wasn’t up, since then there would be some milk. But sometimes she wanted to eat right away when she woke up, and there wasn’t much milk! Thinking back, these were among the most stressful moments of the early days. There isn’t really any scientific advice about this, so your best bet to limit stress may just be to have a concrete plan. Many women report that it works well to choose one feeding, likely in the morning, since that is when the milk is most plentiful, and just pump after that feeding. You’ll get a bit of milk each time, and if you start early, over a week or two you’ll get enough to give a bottle. Then while the kid has that bottle, you can pump another bottle during that feeding. Finally, the main thing women use the pump for is to replace breastfeeding sessions after they’re back at work. The idea is that you pump at approximately the same times the baby would eat, and they eat what you pump the next day. If you are a prolific pumper, you may pump enough extra to freeze.

It is possible to work while pumping, in some cases, and I strongly suggest you get a hands free pumping bra. At a minimum you want to be able to read something on your phone. Many people suggest you try to relax, look at pictures of your baby, and generally wind down while pumping. The idea is that this will increase supply. There is no direct evidence for this; one study of moms pumping for babies in the NICU showed that being near their babies increased milk production, but this is pretty distant evidence. Oh, and while you are spending all your time hooked up to this pump, we should probably say that it’s not as effective as your baby at milk removal. Even a really great pump doesn’t replicate the baby. This varies across women, some women can have no problem fully breastfeeding but literally never get any milk from a pump; others find producing enough milk is no problem.

CHAPTER 6: Sleep Position and Location

The latest recommendations from the American Academy of Pediatrics are starkly opposed to the toy and blanket filled crib. The AAP says infants should sleep alone in a crib (or bassinet) and should be placed in the crib on their back to sleep. There should be nothing in the crib with the baby. Bumpers, pads that wrap around crib slats to prevent little hands or feet from getting stuck, should not be used. Infants should sleep in their own crib or bassinet, not in the parents’ bed, although the crib or bassinet should be in the room with the parents. These recommendations are broadly part of a safe sleep campaign designed to lower the risk of SIDS

Excluding birth defects, SIDS is the most common cause of death for full term infants in the first year of life in the US. By definition, SIDS is the unexplained death of a seemingly healthy infant under a year old, and 90 percent of these deaths occur in the first four months of life. The causes of SIDS are not well understood. It seems to occur when a baby spontaneously stops breathing and doesn’t start again. It is more common in vulnerable infants, premature babies, for example, and in boys.

The medical recommendations to avoid SIDS have four components. Infants should be (1) on their back, (2) alone in the crib, (3) in their parents’ room, and (4) with nothing soft around.

Based on this comparison, the authors argued that babies who sleep on their stomachs are eight times as likely to die of SIDS. This paper also cited overheating as a risk factor, the babies who died were more likely to be wearing heavy clothing to bed, sleeping under a lot of bedding, or sleeping in a hot room. Other research with similar approaches shows the same results. This is not the only type of evidence we have. There is a biological mechanism for the link: babies tend to sleep more deeply on their stomachs, and SIDS risk is increased with deeper sleep.

One note: If your infant does roll over, there is no need to go rolling them back. Once they can do this on their own, the highest risk of SIDS has also passed, probably because the baby now has enough head strength to move their head to breathe more easily.

There is one substantial side effect to back sleeping: deformational plagiocephaly, or, colloquially, flat head. Infants who sleep on their back are at higher risk for head flattening. The frequency of this issue has been rising over time since the implementation of “Back to Sleep.”

This graph also speaks to perhaps the more central question for many families, which is, are there still risks to co sleeping if you do it as safely as possible, that is, if neither parent smokes or drinks a lot, and if the baby is breastfed? The data here says yes. The risk of death for infants who do not bed share in the lowest risk group is 0.08 SIDS deaths per 1,000 births. For those who bed share, it is 0.22 deaths per 1,000 births. Again, we want to put these risks into a broader context. In the US, the overall infant mortality rate is around 5 deaths per 1,000 births. This therefore represents a very small increase relative to the overall mortality rate. A perhaps more useful way to say this is that among families with no other risk factors, roughly 7,100 of them would have to avoid co sleeping to prevent one death.

Notably, there does not seem to be any elevated risk from co sleeping after three months if both parents are not drinking or smoking. Putting these risk analyses together, a main takeaway here is that if you are going to co sleep, you should definitely not drink a lot or smoke, and neither should your partner. Limiting these behaviors will let you co sleep in the safest way possible, although it will not completely eliminate the risks.

While I think one can debate the merits of room sharing at all, given the data, in my view, the AAP’s recommendation that room sharing extend through the baby’s first year is problematic. Why do I say this? The vast majority, up to 90 percent, of SIDS deaths occur in the first four months of life, so sleeping choices after four months are very unlikely to matter for SIDS.

In a 2017 study, researchers evaluated whether a child’s sleeping in a room with a parent made for worse sleep. They found that it did. At four months old, total sleep time was similar for babies sleeping in a parents’ room and those sleeping in their own room, but sleep was more consolidated (i.e., in longer stretches) for those in the latter group. This makes sense: their own room will be quieter. At nine months, infants who slept alone slept longer; this effect was largest for those who slept alone by four months, but also appears for babies who moved to their own room between four and nine months. Most notably, these differences were still present when the child was two and a half years old: children who slept alone by nine months slept forty five minutes more during the night than those who were room sharing at nine months. Sleep is crucial for child brain development; it is not just a selfish parental indulgence.

Related to this, it should be said that if you plan to sleep train your child, success is very unlikely while the child is sleeping in your room. And finally, most people sleep better without a child in the room, and parents being well rested is important, too.

Across virtually all studies of sleep location, the one thing that jumps out as really, really risky is babies sharing a sofa with an adult. Death rates as a result of this behavior are twenty to sixty times higher than the baseline risk. It is not difficult to see why: an exhausted adult falls asleep holding an infant on a cushiony sofa, and it is easy for the infant to be smothered by a pillow. The unfortunate thing is that in at least some of these sofa deaths, the parent involved is trying to avoid the risks associated with bed sharing. They hope that if they sit up, they will stay awake, and then they fall asleep by accident. Even with the small risks of bed sharing, you’d be much better off sharing a bed than accidentally co sleeping on a sofa.

Infants who die of SIDS are more likely to be found with blankets over their heads than control infants. The infant clothing industry has come up with a solution to this, which is the “wearable blanket”, basically, a zipped up bag you put your child in. Since there is no real reason to have another kind of blanket, this recommendation seems like a reasonable one to follow.

CHAPTER 7: Organize Your Baby

In conclusion, many aspects of scheduling will be kid specific, and attempts to organize your baby are likely to meet with some of these variations. But not everything varies. In particular, one thing that doesn’t show as much variation is wake up times. Even at around five or six months, the majority of children wake between six and eight a.m. By the time they get to age two, the range is smaller, six thirty to seven thirty a.m.

The other thing you realize with your second child is that the unscheduled mess of the first year does end. Your baby will, eventually, arrive at a more predictable sleep schedule. Maybe not right away, maybe not exactly the one you envisioned, but they will get there. And this is perhaps the most reassuring thing of all.

CHAPTER 8: Vaccination: Yes, Please

In the 1950s, about five hundred people, mostly children, died of measles each year in the US; 3 to 4 million were sickened. In 2016, zero children in the US died of measles, and there were an estimated eighty six cases. There is a very simple reason for this decline: the development of a measles vaccine. Vaccinations are among the most significant public health triumphs of the past hundred years (public sanitation is another good one, although less controversial). Simply put, millions of lives worldwide have been saved by the introduction of vaccines for diseases like whooping cough, measles, smallpox, and polio. A tremendous amount of discomfort and itching, and also some deaths, have been prevented by the chicken pox vaccine. The vaccine for hepatitis B has reduced liver cancer. Newer vaccines also matter: the HPV vaccine has the potential to significantly lower rates of cervical cancer.

Areas with more educated parents actually have, on average, lower vaccination rates. This suggests it is not necessarily lack of information getting in the way of choosing vaccination. The scientific consensus on vaccinations is extremely clear: vaccines are safe and effective. This conclusion is supported by a very wide range of doctors and medical organizations, and by government and non government entities.

First, for many of the vaccines (all but the DTaP vaccines), there is a risk of allergic reaction. This is extremely rare (about 0.22 in 100,000 vaccines) and can be treated with Benadryl or, in an extreme case, an EpiPen. Allergic reactions account for half the documented risks in the report. Second, fainting sometimes occurs after vaccination, mostly among adolescents. It is unclear what the mechanism is, but fainting does not have long term consequences. This accounts for another two of the convincingly supported risks.

Given this evidence, that we know this to be a risk of the measles virus, and that the children in these three cases weren’t exposed to actual measles, the report concluded that in these cases, it is likely the vaccine caused the disease. This relationship is categorized as “convincingly supports.” It is very important to be clear, though, that this doesn’t mean this is a risk everyone should be concerned about. It arises only for children who are immune compromised, and even then it is vanishingly rare. There are just three case reports in the history of vaccination. If your child has an immune issue, you’ll know, and you’ll talk through vaccination with your doctor. For healthy children, this simply isn’t a risk you should consider in your vaccine calculus. Similar issues arise for immune compromised children who get the chicken pox vaccine. Again, these complications are extremely rare. There is a vaccine link here, but this is far from saying these are scenarios you should be actively worried about it. They are not. There is, finally, one vaccine risk that is more common and, while not serious, can be scary. Specifically, the MMR vaccine is linked with febrile seizures, seizures that occur in infants or young children in association with a high fever. They typically do not have long term consequences, but are very scary in the moment. These are common enough that we can study their relationships to vaccines using large datasets of children. About 2 to 3 percent of children in the US will have a febrile seizure before they are five years old (most of these are not vaccine associated). A number of studies find that these seizures are about twice as likely in the period ten days or so after the MMR vaccine. They are actually more likely for children who get their first MMR dose later (i.e., older than one year); this is a reason to vaccinate on time, rather than to delay.

There are a number of big studies of this relationship. The largest of them includes 537,000 children, all the children born in Denmark from 1991 to 1998. In the Danish data, the authors were able to link vaccination information to later diagnosis of autism or autism spectrum disorders. They found no evidence that vaccinated children are more likely to be autistic; if anything, the results suggest vaccinated children are less likely to be diagnosed with autism. There are many similar studies; some are included in the IOM report, others postdate it. One study focuses on children who have an older sibling with autism and who are therefore more likely to have it themselves. Again, researchers found no link with the MMR vaccine. There is no mechanism by which this would occur, and controlled studies in monkeys also show no plausible relationship. At the end of the day, there is simply no reason to think autism and vaccinations are linked. It is not fair to say there are no risks associated with vaccination at all. Your child may well get a fever. It is also possible (although really quite unlikely) that this fever would lead to a seizure. It is also possible (although, again, very, very unlikely) that they could have an allergic reaction. But it is reasonable to say there is no evidence of significant long term consequences of vaccines for healthy children.

CHAPTER 9: Stay at Home Mom? Stay at Work Mom?

By comparing the outcomes of children who are born in the “six month” maternity leave policy to those born in the “year” policy, we can learn about the effects of maternity leave without worrying about underlying differences across parents. The bottom line from this literature is that these parental leave extensions have no effect on child outcomes. No effects on children’s test scores in school, on income later in life, or on anything else. In many cases, these studies have very long follow up periods. We can say, for example, that one year of parental leave versus two years doesn’t influence a child’s high school test scores or earnings in early adulthood. This evidence focuses on parents working in the first years. If we want to see the impact of parents working when their children are older, we are limited to studies that estimate correlations, not causal impacts. Some studies do exist, though, and when we look for evidence on schooling, test scores, school completion, these correlations tend to be about zero. Two parents working full time has a similar effect to one parent working and one not.

Tying this all together, my view is that the weight of the evidence suggests the net effects of working on child development are small or zero. Depending on your household configuration, these effects could be a little positive or a little negative. But this isn’t the decision that is going to make or break your child’s future success (if there is any decision that would at all).

Childcare is expensive, and most of it is paid in “after tax” income. This means that your income needs to be considerably more than the cost of childcare to break even. To see how this works, think about a family whose total income is $100,000, with each parent making $50,000. This family brings home about $85,000 after taxes. If both parents work and the family pays $1,500 a month for childcare, their total disposable income after childcare is taken into account is $67,000 a year. If one parent stays home, the family makes less (about $46,000 in take home pay), but does not pay for childcare. The difference in take home income is about half what it would be if the couple did not have any children. This calculus becomes more complicated if childcare is more expensive. A full time nanny, especially if you pay the legally required taxes and live in an expensive area, can run to $40,000 or $50,000 a year. For my example family above, that would completely wipe out one parent’s income. They’d be better off financially with one parent staying home.

CHAPTER 10: Who Should Take Care of the Baby?

In economics, we teach people to “solve the tree.” To do this, you work backward from the bottom. First, decide what nanny you would want if you had to have a nanny (in this case, I gave you three choices). Then you’ve solved that leaf of the tree. Then decide what kind of day care you would want if you had to have day care (here, you’ve got four choices). Then compare those two. Now, rather than comparing the wide range of options in each category, you are facing a very specific choice: Do I prefer my “optimal” day care setup or my “optimal” nanny setup?

The authors found that attending higher quality day care strongly correlated with better child language development: kids who went to better day cares seem to talk more. When they looked at behavior problems, though, there did not seem to be a relationship to day care quality in either direction, the effect was about zero. The researchers doing this study followed the children through sixth grade and continued to find that day care quality is associated with better vocabulary outcomes, but not with behavior. It should be clear by this point in the book that there is an obvious issue with this analysis, which is that day care quality also relates to other features of the family. On average, higher quality day care is more expensive, and therefore, a different set of kids are enrolled, kids who, for example, come from better off families. It is therefore hard to know which outcomes to attribute to the family and which to the day care. An advantage of this particular study is the ability to control extensively for family background. They did home visits, so they could evaluate something about the quality of parenting as well. Parenting matters a lot, way more than day care, but their day care results remained even after adjusting for the parenting differences they observed. Of course, concerns remain about the possible role of parental characteristics we do not observe.

First, some basic things. Is the adult (or adults) available and interacting with the children (i.e., are they on their phone, or are they down on the floor with the babies)? Do they have positive physical contact with the children (reinforcing good behavior with a hug, holding the baby)? Then there are some questions on developmental stimulation. Does the adult read to the children? Do they talk to them? Do they respond when the baby makes a noise? (“Gah!” “That’s right, that’s a hippo. Do you want to hold the hippo? Here you go!”) Third, there is behavior. All babies and children act out at various times. The question is, how does the adult respond? Do they respond to negative behavior by physically restraining the child or children involved (the researchers’ question specifically is, do they “restrict them in a physical container”)? Do they hit? Do they speak negatively to the child? These would all be (very) bad signs.

More months in day care before eighteen months are associated with slightly lower cognitive scores by four and a half years old, but more time in care after that is associated with higher cognitive outcomes. It is hard to know why this is. It could be that very early on the one on one attention enhances early language development, but at older ages, children in day care are likely to spend more time on skills like letters, numbers, and social integration than children cared for by nannies or stay at home parents. But this is speculation. It is also possible that these are just correlations, that they are not causal at all. Studies that combine this suggest that, overall, the effect is positive, that kids who are in day care for more time over this entire period have better language and cognitive outcomes at four and a half.

Are kids in day care less attached to their moms? No, they are not. Quality of parenting matters for this, but day care time makes no difference. A final data driven comparison is with illness. Kids who are in day care are more likely to get sick. These are not serious illnesses, more like colds and fevers, stomach flu, and so on. On the plus side, these early exposures seem to confer some immunity, with children who were in day care for more years as toddlers having fewer colds in early elementary school. In all this we come back again and again to two things: First, parenting matters. Much more consistent than any of the associations in these studies is the association between parenting and child outcomes. Having books in your house and reading them to your kid is going to matter much more than what books they have at day care. This seems to be true even though your child probably spends as many waking hours with their care providers as with you. I don’t think we know precisely why this is the case, although it may be that you as the parent are the most consistent influence your child has. Second, childcare quality matters much more than which type of childcare you have. A high quality day care is likely to be better than a low quality nanny, and vice versa. The choice of childcare arrangement is also not just about your child. Ultimately, you have to figure out what works for your family.

First, there is cost. On average, a nanny is more expensive than day care (although this may not always be true). An arrangement where you share a nanny with another family may be a way to offset some of the nanny costs. This is a question for your budget.

Beyond budget, there is the question of convenience. Is there a day care close by (either to home or work), or will you have to drive far out of your way for drop off? And what are your options if your child gets sick? At home, care can still work with a sick kid (also, kids get sick less at home), but day care cannot. What are your backup options? One of the best pieces of parenting advice I got from my friend Nancy was this: Regardless of what childcare you choose, have a plan for who is in charge when the nanny or the kid is sick. Fighting about who will miss work in the moment is a bad idea.

Looking over the data, to the extent we have any evidence day care is worse, it seems to be worse early on in life, say, in the first year or eighteen months. To the extent day care is better, that seems to be truer later in life, say, after a year or eighteen months. Putting this together could argue for a nanny type arrangement (or a helpful grandparent, or some combination of the two) early on, followed by day care at a slightly older age.

CHAPTER 11: Sleep Training

Good news: yes, this method works for improving sleep. There are many, many studies on this, employing a variety of related procedures (many of these are randomized trials). A 2006 review covered nineteen studies of the unfortunately named “Extinction” method, the form of “cry it out” in which you leave and do not return, of which seventeen showed improvements in sleep. Another fourteen studies used “Graduated Extinction”, where you come in to check on the baby at increasingly lengthy intervals, and all showed improvements. A smaller number of studies covered “Extinction with Parental Presence”, in which you stay in the room but let the child cry, and these also showed positive effects. These effects persist through six months or a year in studies that can look this far out. This means that children who are sleep trained are sleeping better (on average) even a year after the training. These methods do not completely solve all sleep problems from day one. And some children respond better than others, as do some parents.

The bottom line is that there is simply a tremendous amount of evidence suggesting that “cry it out” is an effective method of improving sleep. It is worth noting that most of these studies, and, indeed, virtually all sleep books, recommend a “bedtime routine” as part of any sleep intervention. There isn’t much direct evidence on this, the review refers to it as a “common sense recommendation”, but it is generally included with all intervention approaches. The idea is to have some activities that signal to the baby that it is bedtime: putting on the baby’s pajamas, reading them a book, singing some kind of song, turning off the lights.

This finding is consistent across studies. Sleep training methods consistently improve parental mental health; this includes less depression, higher marital satisfaction, and lower parenting stress. In some cases the effects are very large. One small (non randomized) study reported that 70 percent of mothers fit the criteria for clinical depression at study enrollment, and only 10 percent after the intervention. Obviously, we want to think carefully about any possible risks to babies, but the fact that sleep training is good for parents should not be ignored. And sleep is also beneficial to development for babies and kids. Settling into a good sleep routine, one that will ensure longer and higher quality sleep, could have long term positive effects for children.

“Cry it out” works, helps parents and kids sleep better, and improves parental mood and happiness.

A 2006 review of sleep training studies, which included thirteen different interventions, noted the following: “Adverse secondary effects as the result of participating in behaviorally based sleep programs were not identified in any of the studies. On the contrary, infants who participated in sleep interventions were found to be more secure, predictable, less irritable, and to cry and fuss less following treatment.” (Translation: Nothing bad happened in any study, and in most cases, the babies seemed happier after sleep training than before.) More recent studies draw the same conclusion. One interpretation of all these findings is that the babies are better rested, the parents are better rested, and everyone is therefore in a better mood.

Most “cry it out” methods are variants on one of three themes: Extinction, just leave, and do not return; Graduated Extinction, come back at increasingly lengthy intervals; and Extinction with Parental Presence, sit in the room, but do not do anything. Ferber is a proponent of the second, whereas Weissbluth is more in favor of the first. There is evidence that all three methods work, more evidence, perhaps, on the first two than the third, but relatively little evidence on which works best. On the one hand, some reports seem to find that Graduated Extinction is easier for parents and leads to more consistency; other studies have found it prolongs crying. The only general principle from these is that consistency is key. Choosing a method, whichever one, and sticking with it increases success. So the most important consideration here is likely what you think you can do.

Weissbluth, for example, suggests you can begin sleep training as early as eight or ten weeks. At this age, most babies are not able to sleep through the night without eating. You should not expect your two month old to sleep for twelve hours, and you similarly shouldn’t be frustrated or feel like a failure if they do not. The goal of sleep training a ten week old baby is to encourage the baby to fall asleep on their own at the start of the night and then only wake when they are hungry later in the night. On the other hand, a ten  or eleven month old should be able to go through the night without eating, and sleep training babies at that age tends to focus on both their falling asleep on their own and staying asleep through the night. Put simply, the goal of sleep training is not (despite what some would say) to deprive your child of basic needs like food and diaper changes. It is to encourage their going to sleep independently once those needs are met.

CHAPTER 12: Beyond the Boobs: Introducing Solid Food

Children who were exposed to peanuts were far less likely to be allergic to them at the age of five than children who were not. In the group that didn’t get peanuts, 17 percent of children were allergic to peanuts at age five. (Remember, this figure is higher than it would be in the general population because of the way the researchers selected their sample.) However, only 3 percent of the children who were given peanuts were allergic. Since the study was randomized, there was no reason other than the peanut exposure that allergy rates would be different. And these differences showed up in both the high and low allergy risk groups.

Early exposure to peanuts is now the normal recommendation, especially for children at risk for an allergy.

The kids whose moms had eaten more carrots were more likely to prefer the carrot cereal (as evidenced by their consumption and their facial expressions, and presumably also whether they picked up the dish and threw it on the floor). This suggests that flavor exposure, in this case, thorough the placenta and through breast milk, affects whether children are receptive to new flavors. Related to this, once children are starting to eat solid foods, there is randomized evidence that repeated exposure to a food, say, giving kids pears every day for a week, increases their liking of it. This works for fruits, but also for vegetables, even bitter ones. It reinforces the idea that children can get used to different flavors and that they like familiar ones.

Before getting into these, and how you might fix them (hard), you should know that most kids become more picky around two and then slowly grow out of it in their elementary school years. This is sometimes a surprise to parents, your eighteen month old eats like a horse, then all of a sudden around two, they start being very selective and just generally not eating much.

Kids are more likely to try to eat it with what researchers call “autonomy supportive prompts”, things like “Try your hot dog” or “Prunes are like big raisins, so you might like them.” In contrast, they are less likely to try things if parents use “coercive controlling prompts”, things like “If you finish your pasta, you can have ice cream” or “If you won’t eat, I’m taking away your iPad!!”

Putting this together leads to some general advice: offer your very young child a wide variety of foods, and keep offering them even if the child rejects them at first. As they get a little older, do not freak out if they don’t eat as much as you expect, and keep offering them new and varied foods. If they won’t eat the new foods, don’t replace the foods with something else that they do like or will eat. And don’t use threats or rewards to coerce them to eat.

The vast majority of allergies result from eight food types: milk, peanuts, eggs, soy, wheat, tree nuts, fish, and shellfish.

Importantly, although the language here is about “introduction,” these studies include regular exposure as well. It is not enough to have your kid try peanut butter or eggs. You need to actually keep giving it to them regularly. Which leads to the question: How? This is a setting in which going slowly is a good idea. Try a little bit at first, only one allergenic food in a given day, and see how they react. If nothing, give them a little bit more. And so on until you get up to a normal amount.

Soda is strongly discouraged for infants and children (and adults). Your six month old does not need a Coke. Juice is more controversial (and, indeed, I recall a childhood dominated by orange juice), but generally, young children should have formula, breast milk, or (once they start eating solid foods) water.

Choking hazards, nuts, whole grapes, hard candies, are also to be avoided, for obvious reasons. Babies and toddlers do choke, and these foods are more likely to lead to choking. Grapes are okay in pieces, nuts are okay in nut butter form, and hard candies are not recommended for other reasons. Cow’s milk is probably the most complicated recommendation, partly because it interacts with the allergen issues above. It is important to introduce some milk based foods, yogurt, cheese, to avoid allergies. But milk itself is forbidden. The concern is that cow’s milk is not a complete infant nutrition system, and if your infant drinks a lot of milk, it will restrict formula or breast milk intake. In particular, infants who have cow’s milk as their primary milk source are more likely to be iron deficient. The evidence says only that you shouldn’t replace formula or breast milk with cow’s milk. As an addition to, say, oatmeal or cereal, it isn’t a problem.

Finally, honey. The concern with honey is that it could lead to infant botulism. Infant botulism is a serious disease, basically, a toxin interferes with neurological functions, including affecting the infant’s ability to breathe. It is most common under the age of six months and it is treatable, with a very high success rate. Still, the treatment is not easy: the baby typically needs to be hooked up to a breathing machine for a few days until they are able to breathe on their own again. The toxin that causes this, Clostridium botulinum, is found in soil and elsewhere, including in honey. This, combined with the fact that there were multiple case reports from the 1970s and ’80s in which infants who developed botulism had consumed honey, led to the recommendation against honey through the first year of life (sometimes even two or three).

The general wisdom of vitamin supplementation (for anyone, adults, children, babies) is complicated. It is true that if you are deficient in particular vitamins, it can cause serious problems. Vitamin D deficiency causes rickets. Vitamin C deficiency famously causes scurvy, as was first recognized in sailors who went months without eating any fresh vegetables or fruit. However, if you eat a typical varied diet, even one that’s pretty unhealthy by many standards, you are very unlikely to be seriously deficient in any of these vitamins. Your toddler or young child does not generally need a multivitamin (no Flintstones gummies for them). If they eat only a very limited diet, it is possible a multivitamin would be necessary, but this would be unusual. Even a child who seems like a very picky eater will be getting enough vitamins to sustain them. A baby who is breastfed will get most vitamins this way as well. The two possible exceptions to this are vitamin D and iron. Vitamin D is not present in many foods, and is not present in high concentrations in breast milk. People do get vitamin D through sun exposure, but since many of us live in houses in cold places and not on the savanna, sun exposure isn’t always consistent. As a result, a lot of infants and children are considered deficient in vitamin D. This could be as much as a quarter or more of white children, and higher among children of color (darker skin lowers vitamin D absorption from the sun). Deficiency here is defined as having a blood concentration of vitamin D below some cutoff level. What is less clear is whether this really has much actual health impact. Relatively few studies have looked at the actual outcomes associated with vitamin D, like bone growth. In two that did, very small randomized trials of supplementation, there were no impacts on bone growth or bone health, even though supplementation did increase the concentrations of vitamin D in babies. This isn’t to say you shouldn’t use vitamin D supplements. And certainly rickets does occur, primarily in developing countries with serious nutritional limits. But it does suggest that if you miss a day here or there, you shouldn’t panic.

PART THREE: FROM BABY TO TODDLER

CHAPTER 13: Early Walking, Late Walking: Physical Milestones

Milestones:

9 months: Rolling both sides, sitting with support, motor symmetry, grasping and transferring objects between hands.

18 months: Sitting, standing, and walking independently; grasping and manipulating small objects.

30 months: Subtle gross motor errors, looking for loss of previous skills (marker of progressive disease).

The 9 and 18 month milestones are the most crucial here; by 30 months, most major issues have been well identified, and doctors are looking for smaller things.

Milestone Range:

Sitting without support 3.8 months to 9.2 months

Standing with assistance 4.8 months to 11.4 months

Crawling (5% of kids never do) 5.2 months to 13.5 months

Walking with help 5.9 months to 13.7 months

Standing alone 6.9 months to 16.9 months

Walking alone 8.2 months to 17.6 months

Kids younger than school age get an average of six to eight colds a year, most of them between September and April. This works out to about one a month. These colds last on average fourteen days. A month is thirty days. So in the winter, on average, your kid will have a cold 50 percent of the time. On top of this, most kids end their cold with a cough that can last additional weeks. It adds up. Most colds are minor, although they increase the risk of ear infection and other prolonged bacterial infections (bronchitis, walking pneumonia), which is why most doctors will tell you to come in if you are concerned, or if a fever lasts longer than a couple of days, or if your child gets worse after they’ve seemed to get better. Of these complications, ear infections are the most common. About a quarter of kids will have an ear infection by the age of one, and 60 percent by the age of four.

One thing that has changed since we were children: antibiotics. It used to be common to prescribe antibiotics for cold symptoms, at least some of the time. Not anymore. Colds do not respond to antibiotics (they are caused by a virus), and your doctor shouldn’t (and typically won’t) prescribe them. Globally, overuse of antibiotics is a public health problem, since it contributes to antibiotic resistance. And even for your particular kid, antibiotics aren’t totally risk free, they can contribute to diarrhea, for example. The move toward prescribing antibiotics sparingly is definitely a good thing.

CHAPTER 14: Baby Einstein vs. the TV Habit

In the case of Sesame Street, there is actually good research suggesting that exposure to the show increases school readiness in kids ages three to five.

In all three age groups, when kids watched an actual person doing the action, some of them were able to replicate it a day later. The video demonstration was much less successful, the twelve month olds learned nothing, and the older kids learned much less than from seeing a live person do it. Another example is a study where researchers tried to use a DVD recording to maintain exposure to non native sounds. At birth, children are able to learn the sounds from any language, but as they age, they specialize in the sounds they hear regularly. Researchers tried to maintain exposure of English speaking nine to twelve month olds to Mandarin language sounds, either through a live person or through a DVD. The live person worked well, the DVD did not.

The study’s authors noted that the most significant predictor of both how many words the children spoke and how fast their vocabularies grew was whether their parents read them books. Other authors have extended versions of this study to kids up to age two and found similar results.

Kids learn songs from movies and from shows, and can pick up names of characters and basic plot elements. Researchers in the lab have shown that three to five year old kids are able to learn words from television.

Early on, researchers used randomized trials to evaluate the effects of Sesame Street. In one evaluation, the group of families assigned to the treatment group had their televisions hooked up so they could access the show more effectively. The researchers found, over a period of two years, improvements in various measures of school readiness, including vocabulary. The effects of Sesame Street seem to be long lived. A more recent study looked back at the early years of the show and compared the kids who got early access to it, because of better TV reception, to those who got later access. The earlier access kids were less likely to be held back in school at older ages. The show had bigger positive effects for children from more disadvantaged backgrounds, which could be due to differences in the other activities in their day, or to something else. All this is to say that for slightly older children, television can be a source of some learning; this argues (among other things) for curation of what they watch.

The authors reported the differences among the groups in math, reading, and vocabulary test scores at age six. Their results suggest that watching more TV under the age of three lowers test scores; not a huge amount, but by the equivalent of a couple of IQ points. If you are looking in this data for evidence that TV is bad, which is what the authors argue, high watching before age three seems to be an issue. However, watching TV at older ages doesn’t seem to matter. When the authors compared, say, the kids who watched only a little TV before age three and then a lot between ages three and five to the children who watched little TV before age three and little later, they found their test scores to be no different. If anything, the kids who watched more TV later had higher test scores than those who watched less.

The actual data we have on these questions is pretty limited. Based on what is available, I’d say we can learn a few things: Children under two years old cannot learn much from TV. Children ages three to five can learn from TV, including vocabulary and so on from programs like Sesame Street. The best evidence suggests that TV watching in particular, even exposure at very young ages, does not affect test scores.

If the alternative to an hour of TV is a frantic and unhappy parent yelling at their kid for an hour, there is good reason to think the TV might actually be better.

CHAPTER 15: Slow Talking, Fast Talking: Language Development

Early talking doesn’t guarantee later success, even at four, and late talkers mostly look like everyone else within a few years.

CHAPTER 16: Potty Training: Stickers vs. M&M’s

An eighteen month old is much less likely to simply decide they will not poop in the potty no matter what you say. They have less will to defy you. This may make littler kids easier. On the other hand, a three year old can be reasoned with and, yes, bribed. They have more will to defy you, but you can also take advantage of their better ability to understand and control themselves. That may make them easier to deal with.

On the other side is a more laissez faire approach, where you more or less let the child lead with the timing that works for them. This approach involves looking for signs of readiness and encouraging toilet use when they become apparent. This is goal oriented in the sense that ultimately you would like the child to use the toilet, but it does not work on the same time frame.

You will try anything, literally anything!, to get your child to use the bathroom, but you cannot actually force them. And, probably most important, all kids are different. Some kids respond to stickers. Some respond to M&M’s. Maybe some respond to meatballs. The bottom line is that potty training is really all about what works for your family and your kid. The evidence on changes over time suggests it is possible to train your child at a younger age than is now typical, if you want to. To do this, you’ll probably have to adopt a more goal oriented approach (rather than a child led approach). Or you can wait until your child decides they are ready, which will probably be when they are closer to three years old or even a bit older. The child led approach to training may take longer, but it also may be more pleasant for you.

Doctors generally do not worry about lack of nighttime dryness until a child is six years old.

CHAPTER 17: Toddler Discipline

Before even getting into evidence, though, it’s worth stepping back and thinking about why we want to discipline our kids. What are we trying to accomplish? I think the answer is the same as what we are trying to do with all our other parenting choices: we are trying to raise happy, nice, productive adults. When my kid refuses to clean up a mess and I discipline that behavior, it is not really that I want some help cleaning up. Actually, it would be faster to clean up myself than get her to do it. It’s more that I’m trying to teach her to be someone who takes responsibility for her messes, both the LEGO messes now and the inevitable non LEGO messes she’ll create in the future. This is the discipline as education philosophy espoused by French parenting (thanks, Bringing Up Bébé!). Discipline is not the same as punishment. Yes, there is a punishment component. But it’s in the service of raising better humans, not punishment for its own sake.

There are a number of evidence based parenting interventions. These include 1 2 3 Magic, the Incredible Years, Triple P Positive Parenting Program, and so on. Many schools, including those that have children with serious behavioral issues, use a similar program called Positive Behavior Interventions and Supports, which has a similar set of goals and structures.

Toddler discipline is, really, parental discipline.

For example, 1 2 3 Magic develops a system of counting (to three, obviously) in the face of disruptive behavior, and if three is reached, there is a defined consequence (a time out, loss of a privilege, etc.). Finally, there is a strong emphasis on consistency. Whatever the system you use, use it every time. If the consequence of counting to three is a time out, then there needs to be a time out every time, including, say, in the grocery store. (The book suggests you find a corner of the store, or bring a “time out mat” with you.) As an extension, if you say no to something, you stick to no. If your kid asks for dessert and you say no, you cannot then later say yes if they whine for long enough. This basically makes sense, what do they learn from that? That whining will sometimes work. Let’s do more of it! And similarly, do not make threats you cannot carry out.

I’ll talk about spanking in a bit, but the evidence suggests that it has negative consequences in both the short and long term. So if hitting is the alternative, then one of these programs is probably worth a try.

One of the main tenets of these parenting approaches is that discipline should be reserved for actual bad behavior, not for things that are merely annoying.

The authors argued that spanking does have negative long term impacts, especially on behavior problems. Spanking at age one increased behavior problems at three, and spanking at three increased behavior problems at five. These results held even with controls for earlier behavior, spanking at three relates to behavior problems at five, even controlling for behavior problems at three.

There is correspondingly no evidence that spanking improves behavior.

CHAPTER 18: Education

We can begin with a well established fact. There is a large body of literature showing that children whose parents read to them as babies and preschoolers have better performance on reading tests later.

Rather than just reading a book, kids benefit from being asked open ended questions: “Where do you think the bird’s mother is?” “Do you think it hurts Pop when the kids hop on him?” “How do you think the Cat in the Hat is feeling now?”

Is it a good idea to put your child in preschool? We can look for some evidence on this by thinking back to the chapter on day care. The evidence I discussed there showed that more time in day care after eighteen months or so was associated with better language and literacy development at slightly later ages. This is about the best evidence we have that preschool might be a good idea.

This means that many of the “quality” measures we discussed in the day care section apply here, too, is the area safe, do the adults seem engaged, etc.

A related question is whether you should favor one preschool “philosophy” over others. The three philosophies you will most commonly encounter in your preschool exploration are Montessori, Reggio Emilia, and Waldorf. Montessori education focuses on a particular classroom structure and a set of materials. There is an emphasis, even in young children, on the development of fine motor skills. These schools generally refer to children’s play as “works.” Young children are typically exposed to letters and numbers and writing them in sand, counting blocks, and so on. Reggio Emilia inspired schools put more emphasis on play, with typically little formal letter or number exposure at preschool ages. (One Reggio Emilia style preschool I visited told me they explicitly do not spend any time on letters for the three  and four year old class, and wouldn’t even display letter cards around the room. This seemed a little extreme.) The Waldorf schools have a heavy outdoor component and, similar to Reggio Emilia, are largely play based. The Waldorf principles focus on learning through play and art, and tend to also have some domestic activity component (cooking, baking, gardening).

All three methods have a structured day, so kids know what to expect when. They all acknowledge that young kids benefit from being able to explore in a safe environment and to self direct, to some extent, in what they do.

All this is to say that, again, we simply do not have a lot of concrete data to guide you. Further complicating both research and decision making, it is possible, even likely, that the best type of preschool will vary by individual child.

PART FOUR: THE HOME FRONT

CHAPTER 19: Internal Politics

“In sum, parenthood hastens marital decline… .” It is worth noting that these studies do tend to find that people who are happier before they have kids recover better, and that planned pregnancies are less impactful than unplanned ones. And the effects are not enormously large. Many people are still, on net, happy with their spouse. Just, you know, slightly less.

Being aware of this may be helpful, and in this chapter I talk about some proposed solutions to the marital happiness problems. But before doing that, it’s useful to look at two specific things that researchers have speculated play a role in the marital happiness decline. The first is unequal chore allocation: women tend to do the bulk of household work, even if they also work outside the home. The second is a decline in sex: parents have less sex, and sex makes people happy.

Sleep is a key issue. Drops in marital satisfaction are higher in couples with kids who sleep less. Lack of parental sleep contributes to depression (in both parents) and correspondingly to less happy marriages. You need sleep to function, and sleep deprivation affects your mood. If you are cranky, you’re cranky with your partner.

Some small scale randomized interventions do show some effectiveness. One is the “marriage checkup.” The idea behind this is to have an annual meeting, possibly facilitated by some professional, to actually discuss your marriage. What do you feel is working? What isn’t working? Are there particular areas of concern or unhappiness? These checkups seem to result in improvements in intimacy (i.e., sex) and marital satisfaction. This makes sense in the abstract; it’s helpful to talk things through methodically with a neutral third party. Beyond this particular intervention, there is other evidence in favor of therapy more generally, group couples therapy, counseling programs beginning before birth and continuing after, to improve relationships. Speaking in broad generalizations, these focus on communication and positive solutions to conflict.

CHAPTER 20: Expansions

When researchers performed this analysis, they found that for the older child, test scores were higher if there was more space between that child and their younger sibling. This may reflect, for example, more parental time invested in reading or other skill development at young ages. These effects, though, were pretty small.

I think the bulk of the evidence suggests there are some small risks, both short and possibly long term, to very short birth intervals. So waiting until the first child is at least a year old to get pregnant again may be a good idea. It also just may be easier on you as a parent, given the intensity of the infant stage.

CHAPTER 21: Growing Up and Letting Go

Parenting cannot be about thinking about every possible eventuality, every possible misstep. Sometimes, you just need to let it go. So, yes, it makes sense to take parenting seriously, and to want to make the best choices for your kid and the best choices for you. But there will be many times that you need to just trust that if you’re doing your best, that’s all you can do. Being present and happy with your kids is more important than, say, worrying about bees. At the end, let’s raise a glass to using data where it’s useful, to making the right decisions for our families, to doing our best, and, sometimes, to just trying not to think about it.

Key Takeaways from Each Chapter:

Newborn baths early on are unnecessary, but not damaging. Tub baths are better than sponge baths. Circumcision has some small benefits and also carries some small risks. The choice is likely to come down largely to preference. Rooming in doesn’t have any compelling effects on breastfeeding outcomes either way. It is worth being careful about falling asleep with your infant if you choose to keep them with you at all times. Infant weight loss should be monitored and compared with expectations; you can do this yourself at www.newbornweight.org. Jaundice is monitored with a blood test and should be treated if outside the normal range; you can monitor this yourself at www.bilitool.org. Delayed cord clamping is likely recommended, especially if your baby is premature. Vitamin K supplements are a good idea. Eye antibiotics are likely unnecessary for most babies but are mandated in some states and have no known downsides.

Swaddling has been shown to reduce crying and improve sleep. It is important to swaddle in a way that allows the baby to move its legs and hips. Colic is defined as excessive crying. It is self limiting, meaning it will stop eventually. Changing formula or maternal diet, treatment with a probiotic, or both have shown some positive impacts. Collecting data on your baby is fun! But not necessary or especially useful. Exposing your infant to germs early on risks their getting sick, and the interventions for a feverish infant are aggressive and typically include a spinal tap. Limiting germ exposure may be a good idea, even if just to avoid these interventions.

It takes time to recover from childbirth. You’ll bleed for several weeks. You may have vaginal tearing, which takes a few weeks to heal. A caesarean section is major abdominal surgery, and it will take significant time for you to be mobile again afterward. Return to exercise depends a bit on your birth experience, but you can typically start within a week or two, and most women could be back to their pre pregnancy routine by six weeks. There is no set waiting time for sex, although you should wait until you’re ready (and are on birth control if you’re not ready for another child). Postpartum depression (and related conditions) are common and treatable. Get help as soon as you need it.

There are some health benefits to breastfeeding early on, although the evidence supporting them is more limited than is commonly stated. There are likely some long term health benefits, related to breast cancer, for Mom. The data does not provide strong evidence for long term health or cognitive benefits of breastfeeding for your child.

Breastfeeding can be very hard! On early interventions: Skin to skin contact early on can improve likelihood of breastfeeding success. On latching: Nipple shields work for some women, although they can be hard to quit. There is very limited evidence that fixing a tongue tie or lip tie can improve nursing. On pain: Fixing a tongue tie can improve pain for Mom. There isn’t much evidence on how to fix nipple pain, but focusing on the latch may help. If you are still in pain a few minutes into a feeding, or a few weeks into nursing, get help; it could be an infection, which would be treatable, or some other problem with a solution. On nipple confusion: Not supported in the data. On milk supply: The majority of women will have their milk come in within three days after the baby’s birth, but for about a quarter, it will take longer. The biological feedback loop is compelling: nursing more should produce more supply. Evidence on the effectiveness of non drug remedies (e.g., fenugreek) on supply is limited. On pumping: It sucks.

There is good evidence that infants who sleep on their back are at lower risk for SIDS. There is moderate evidence that bed sharing is risky. These risks are much higher if you or your partner smokes or drinks alcohol. There is some less good evidence that room sharing is beneficial. The benefits to room sharing die out in the first few months. Infant and child sleep may be better if your child sleeps alone after the first few months. In the crib: Wearable blanket: check! Bumpers: very small risk, although small benefits as well. Sleeping on a sofa with an infant is extremely dangerous.

There are some broad guidelines for sleep schedule. Longer nighttime sleep develops around two months. Move to three regular naps around four months. Move to two regular naps around nine months. Move to one regular nap around fifteen to eighteen months. Drop napping around age three. There is tremendous variability across children, which you mostly cannot control. The most consistent schedule feature is wake up time between six and eight a.m. Earlier bedtime = longer sleep.

Vaccinations are safe. A very small share of people have allergic reactions, which are treatable. There are some extremely rare adverse events, most of which occur in immune compromised children. The only more common risks are fever and febrile seizures, which are also rare and do not do long term harm. There is no evidence of a link between vaccines and autism, and much evidence to refute such a link. Vaccines prevent children from getting sick.

Babies benefit from their mothers taking some maternity leave. However, there is little evidence suggesting that having a stay at home parent after the parental leave period has either good or bad consequences for children. Decisions about whether to have a parent stay home should consider your preferences, along with consequences for your family budget in both the short and long term. Stop judging people!

With any childcare arrangement, quality matters. For day care, in particular, you can use some simple tools to try to do your own quality evaluation. On average, more time in day care centers seems to be associated with slightly better cognitive outcomes and slightly worse behavior outcomes. The positive effects of day care present more at older ages, the negative ones more at younger ages. Kids in day care get sick more, but develop more immunity. Parenting quality swamps childcare choices in its importance, so make sure you pick something that works for you as a parent as well.

“Cry it out” methods are effective at encouraging nighttime sleep. There is evidence that using these methods improves outcomes for parents, including less depression and better general mental health. There is no evidence of long  or short term harm to infants; if anything, there may be some evidence of short term benefits. There is evidence of success for a wide variety of specific methods, and little to distinguish between them. The most important thing is consistency: choose a method you can stick with, and stick with it.

Early exposure to allergens reduces incidences of food allergies. Kids take time to get used to new flavors, so it is valuable to keep trying a food even if they reject it at first, and early exposure to varying flavors increases acceptance. There is not much evidence behind the traditional food introduction recommendations; no need to do rice cereal first if you do not want to. Baby led weaning doesn’t have magical properties (at least not based on what we know now), but there is also no reason not to do it if you want to. Vitamin D supplementation is reasonable, but don’t freak out about missing a day here and there.

Delayed motor development can be a signal of more serious issues, the most common of which is cerebral palsy. Variation in motor development within the (very wide) normal range is not a cause for concern. There are many approaches to evaluating motor skills; your pediatrician is your best partner in doing so. Children get many, many colds, about one per month for the winter, at least until school age. Lotion tissues. Lots of lotion tissues.

Your zero  to two year old cannot learn from TV. A three  to five year old can learn from TV. It is worth paying attention to what they are watching. The evidence is sparse overall. When in doubt, use your “Bayesian priors” to complement the data.

There are some standard tools to determine child vocabulary size, which you can use on your own. There are also some metrics you can compare. Girls develop language faster than boys, on average, although there is a lot of overlap across genders. The timing of language development does have some link with later outcomes, test scores, reading, but the predictive power is weak for any individual child.

Age at toilet training has increased over time, very likely as a result of parents choosing to train later. Starting training earlier leads to earlier completion on average, although it generally takes longer; starting intensive training before twenty seven months does not seem to lead to earlier completion. There is little evidence on the efficacy of child led training versus more intensive, goal oriented methods. Refusal to poop on the toilet is a common complication with some limited solutions.

There are a variety of programs that have been shown to improve children’s behavior. These focus on consistent rewards and punishments, and avoiding parental anger. Examples include 1 2 3 Magic and the Incredible Years, among others. Spanking has not been shown to improve behavior and, indeed, has been associated with worse behavior in the short term and even through adulthood.

There is some support for the value of reading to your children starting in infancy. Your baby cannot learn to read. Whether your two  or three year old can is unclear, but it would be very unusual for them to be a fluent reader. Evidence on the value of different preschool philosophies is limited.

Marital satisfaction does decline, on average, after children. These declines are smaller and briefer if you’re happier before children, and if the kids are planned. Unequal division of labor and less sex probably do play some role, although it is hard to get a sense of how important these are. There is some small scale evidence suggesting marital counseling and “marriage checkup” programs can improve happiness.

The data doesn’t provide much guidance about the ideal number of children or birth interval between them. There may be some risks to very short intervals, including preterm birth and (possibly) higher rates of autism.