Introduction — The Data Behind the Decisions
One of the great themes of your parenting life is that you have way less control than you think you do. This is also, it turns out, one of the great problems for learning from the data. Studies of breastfeeding show time and again that breastfed children have better school performance and lower obesity rates — but these outcomes are also linked with a mother’s education, income, and marital status. How can you know whether it is the breastfeeding or those other differences that is causing the better outcomes? One answer is that some data is better than other data. Using an economist’s training — especially the part focused on teasing causality out of data — it becomes possible 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, but it is 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. And your choices can be right for you and also not the best choices for someone else. 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, it offers the necessary inputs and a decision framework. The data is the same for us all, but the decisions are yours alone. The goal 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 are happy with your choices, that is the path to happier, more relaxed parenting — and, hopefully, to a bit more sleep.
Chapter 1 — The First Three Days
A hospital bath is not a terrible thing, but there is also really no reason to bathe your newborn other than the gross-out factor. Most of the blood can simply be wiped off. Many families wait a week or two before giving a real bath at home, and no harm comes from that — we never bathed Finn in the hospital at all and still waited the family standard two weeks to give him a bath at home. Circumcision can be done more or less as soon as you confirm that the penis is working properly — after the first time the baby pees. The American Academy of Pediatrics suggests the health benefits of circumcision outweigh the costs, but notes correctly that both benefits and costs are quite small. This decision often comes down to personal preference, cultural considerations, or simply a desire to have your son’s penis look a particular way. All of these are valid reasons to do it or not do it.
If you have the option to send your baby to the nursery for a few hours and you want to do that, you should feel no shame in doing so. There is no good evidence that you are disrupting your breastfeeding relationship. And if you find yourself falling asleep with the baby in the bed, ask for help.
Newborn weight loss is common and closely watched. The researchers behind one careful study created a website, newbornweight.org, where you can enter the time of birth, method of birth, method of feeding, birth weight, and current weight to learn where your child falls in the distribution. The major concern with weight loss is that it signals dehydration — but this is something you can monitor directly. If your baby is peeing with some frequency and does not have a dry tongue, there is a very good chance they are not dehydrated. If you do see those signs, supplementation may be a good idea even if the weight loss itself is not severe. For jaundice, a website called bilitool.org will tell you whether treatment is recommended given your baby’s bilirubin level.
On cord clamping, the evidence increasingly favors delaying the cut if possible. For premature infants the data supporting a delay is particularly strong, and on balance the recommendations now favor it for all newborns.
Chapter 2 — Wait, You Want Me to Take It Home?
There are a variety of blankets that allow you to swaddle a baby so they cannot escape. The key is that these have some mechanism for keeping the baby tucked in other than folding — many yards of fabric or some Velcro. One widely used option is the Miracle Blanket. Whatever you choose, it is crucial to swaddle in a way that allows the baby to move their legs and flex at the hip; the risk of hip dysplasia arises specifically when those movements are restricted.
The most important thing to do when a baby cries constantly is to try to take care of yourself. Infant crying is linked to postpartum depression and anxiety in both parents, and both parents will need a break. The cause of colic is poorly understood, which makes solutions hard to develop. Many of the theories involve digestion — poorly developed gut flora or an intolerance to milk protein — and most proposed solutions follow from those theories. Two treatments have shown some known success. One is supplementation with a probiotic, which a number of studies have shown to reduce crying. The other is managing the baby’s diet, either by changing formula types or, if the baby is breastfed, by changing the mother’s diet. Switching to a soy-based or hydrolyzed protein formula is one recommendation — most major formula makers, including Similac and Enfamil, have versions of these. The evidence on formula switching is largely financed by formula companies, so take it for what it is, but it may be worth a try. If breastfeeding, the standard recommendation is elimination of all dairy, wheat, eggs, and nuts — a pretty dramatic change. Unfortunately, we do not know whether one food, all of them, or some combination makes the difference, and the evidence overall is limited.
If you want to collect data and make graphs about your baby, go for it — but remember that this is the illusion of control, not actual control. As your child ages into toddlerhood and beyond, wiping down everything with hand sanitizer or bringing disposable placemats to restaurants is probably not necessary. Going a bit more in the exposure direction may actually be sensible. Your kid probably should not lick the floor at the airport, as some children occasionally do, but moderate germ exposure after infancy seems fine. Doctors are reasonably lax about germ exposure once a baby is a few months old — the reason they are not lax in the first couple of months is that the smaller the child, the more vulnerable they are to serious complications, and for very young infants, especially those younger than twenty-eight days, medical protocols call for 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 after delivery, depending on how traumatic the birth was, and stool softeners are commonly given to ease the first postbirth bowel movement.
A few days later you are home. The most immediate consequences — heavy bleeding, uncomfortable first pee — will be over, but you will not feel normal. You will still look pregnant for a few days or weeks. Then you will have a stretch of floppy skin, which does resolve eventually — by which I mean weeks or months later, not days. Even once the floppy skin is gone, many women find they have what is referred to as “mummy tummy,” a pouchy stomach that never quite snaps back. Once you can exercise, it can be challenging to find time, but if it is important to you, you should try. Exercise can help combat postpartum depression and generally improves mood.
Sex after childbirth can be painful. Breastfeeding promotes vaginal dryness and lowers sex drive, and injuries during birth can have persistent effects — you want to take it slow. Most women need some lubrication the first few times. Other activities, oral sex either given or received, may be easier to restart and more enjoyable early on. And many women, after having a small person attached to them nearly constantly, really do not want to be touched. That is normal.
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 called the “baby blues” and is self-limiting: 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, when it extends beyond baby blues, proceeds in stages. For mild depression, the first line is to try to manage without drugs. There is some evidence that exercise or massage can be helpful. Perhaps most important is sleep — for new parents, lack of sleep can be a huge contributor to mild depression.
Chapter 4 — Breast Is Best? Breast Is Better? Breast Is About the Same?
We know breast milk contains antibodies, so it is plausible that it is protective against some illnesses. The most compelling study found two significant impacts: in the first year, breastfed babies had fewer gastrointestinal infections, meaning diarrhea, and lower rates of eczema and other rashes. It seems reasonable to conclude that breastfeeding lowers infant eczema and gastrointestinal infections. For other illness outcomes, the most compelling evidence is in favor of a small reduction in ear infections in breastfed children. SIDS is rare — about one in every 1,800 births, and perhaps one in 10,000 among babies with no other risk factors. Ear infections and colds, by contrast, are common; your kids will get colds whether you breastfeed or not.
It is certainly true that obesity and breastfeeding are correlated — kids who are breastfed are less likely to be obese later in life. But this correlation does not show causation. It does not prove that kids who go on to become obese do so because they were not breastfed.
On the question of IQ, one important study proceeded in three phases. First, comparing breastfed and non-breastfed children with simple controls, researchers found large differences in child IQ between the groups. In the second phase, they added an adjustment for the mother’s IQ, and found that much of the breastfeeding effect disappeared, though a smaller one persisted. Then came the crucial third phase: comparing siblings born to the same mother, one breastfed and one not. This approach accounts for all the differences between mothers, not just the ones captured by an IQ test. In this sibling analysis, breastfeeding had no significant impact on IQ. The conclusion is that it is something about the parents, not anything about breast milk, that drives the association seen in simpler analyses. There is no compelling evidence for smarty boobs.
One reason the hype persists is that people 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 limited knowledge of statistics, and there is no pressure on the media to focus on the best studies.
For some women, breastfeeding is empowering and happy — it is convenient to have a ready food source anywhere they go, and they find nursing their baby to be a peaceful and relaxing time. For others, breastfeeding makes them feel like a cow. They hate lugging the breast pump around. It is hard to tell if the baby is even getting enough food. Their nipples hurt. Many of the purported benefits for moms are really subjective. One of the things on every pro-breastfeeding list is “saves money” — but 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 importantly, there is your time, which is valuable. I recall one particular experience pumping in the bathroom at LaGuardia Airport when the whole thing seemed like a farce.
There is one benefit with a larger and more robust evidence base: the link between breastfeeding and breast cancer. Across a wide variety of studies and locations, there seems to be a sizable relationship — perhaps a 20 to 30 percent reduction in the risk of breast cancer. Since almost one in eight women will have a form of breast cancer at some point in their lives, this reduction is big in absolute terms. The data is not perfect — controls for maternal socioeconomic status are almost always missing — but the case for causality is bolstered by concrete mechanisms: breastfeeding changes some aspects of the cells of the breast, making them less susceptible to carcinogens, and it lowers estrogen production, which in turn can lower breast cancer risk. After all that focus on benefits for the child, it may be that the most important long-term impact is actually on Mom’s health.
The most convincing personal case for breastfeeding comes from women who have done it and describe the satisfaction of closeness with their child — something no one else can give them. This is a great reason to try, and a good reason to support women who want to, and to not shame women who breastfeed in public. But it is not a good reason to judge yourself if you decide breastfeeding is not for you.
Chapter 5 — Breastfeeding: A How-To Guide
Moms who had their infants skin-to-skin after birth were more likely to still be breastfeeding at six weeks — 72 percent versus 57 percent — and also reported less pain while being stitched up after birth. Despite the warnings you may hear, 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. The only food women are medically advised to avoid during breastfeeding is high-mercury fish — no swordfish, king mackerel, or tuna. But other fish are fine, as are unpasteurized cheeses, sushi, rare steak, and deli meats. If your baby is suffering from colic, there is some evidence that avoiding common dietary allergens could help. There is something of an old wives’ tale that gassy foods like cauliflower, broccoli, and beans lead to a gassy baby — there is only one paper on this, and it is based on a mail survey with such serious problems in data collection and analysis (poor response rate, excessive response among people hyperconcerned about breastfeeding, problems with statistical precision) that it is safe to ignore it. Eat what you want.
Many women hear, often from the internet, that they should avoid alcohol altogether while breastfeeding, or that if they drink at all they should “pump and dump.” On the other side, some say beer will increase milk supply. Neither is really true. 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 exposure is extremely low. One paper carefully calculated that even if you had four drinks very quickly and then breastfed at peak blood alcohol level, the baby would be exposed to only a very, very low concentration — extremely unlikely to have any negative effects. On the flip side, drinking does not improve your milk supply; if anything, it may lessen it a bit.
Most medications are generally safe while nursing, and you can search virtually any drug in the LactMed database online. The first line of defense for postbirth pain is Tylenol or ibuprofen, which are well tolerated and fine while breastfeeding. However, ibuprofen is not always enough, especially after a C-section. Codeine used to be a common next step, but more recent data shows it has significant nervous system effects in babies — making them extremely sleepy, with a few cases of severe consequences — and newer recommendations generally advise against codeine or other opioids like oxycodone for breastfeeding mothers. If you have been on antidepressants before and know which one works for you, use that one. If not, the first-line SSRIs for nursing mothers are paroxetine and sertraline, which transfer to breast milk at the lowest levels. As for caffeine, most people find it is fine while nursing, and there is no literature suggesting risks to the baby, though some babies are quite sensitive and get fussy and irritable. If that is the case, you may have to avoid it.
There are basically three reasons to use a breast pump. First, if you are struggling with low supply early on, your doctor may suggest pumping after feedings to increase supply — the theory is sound, though there is not much empirical evidence. Second, many women pump early on to start giving the occasional bottle or to build a supply before returning to work. Many women report that it works well to choose one feeding — likely in the morning, when milk is most plentiful — and pump after that feeding; over a week or two you will get enough to give a bottle. Third, the main use is to replace breastfeeding sessions after returning to work: you pump at approximately the same times the baby would eat, and they eat what you pumped the next day. A hands-free pumping bra is essential — at minimum you want to be able to read something on your phone. Some suggest relaxing and looking at pictures of your baby to increase supply; there is no direct evidence for this, though one NICU study showed that proximity to the baby helped. And even a great pump is not as effective as your baby at milk removal — some women who breastfeed successfully never get any milk from a pump, and that variation is normal.
Chapter 6 — Sleep Position and Location
The latest recommendations from the American Academy of Pediatrics call for a bare crib. Infants should sleep alone in a crib or bassinet, on their back, with nothing else in the crib — no bumpers, no blankets. The crib should be in the parents’ room. These recommendations are part of a safe sleep campaign designed to lower the risk of SIDS, which is the unexplained death of a seemingly healthy infant under one year old. Excluding birth defects, SIDS is the most common cause of death for full-term infants in the first year of life in the US. Ninety percent of SIDS deaths occur in the first four months. It is more common in premature babies and in boys.
The medical recommendations to avoid SIDS have four components: infants should be on their back, alone in the crib, in their parents’ room, and with nothing soft around. Research shows that babies who sleep on their stomachs are roughly eight times more likely to die of SIDS. There is also a biological mechanism: babies tend to sleep more deeply on their stomachs, and SIDS risk is increased with deeper sleep. Overheating is also a risk factor — babies who died were more likely to be wearing heavy clothing, sleeping under a lot of bedding, or sleeping in a hot room. One note: if your infant rolls over on their own, there is no need to roll them back. Once they can do this, 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 of back sleeping: deformational plagiocephaly, or flat head, which has been rising since the implementation of “Back to Sleep.”
Even in the lowest-risk group — neither parent smokes or drinks heavily, baby is breastfed — co-sleeping carries some elevated risk. The risk of SIDS death for infants who do not bed-share in this group is 0.08 per 1,000 births; for those who bed-share, it is 0.22 per 1,000 births. The overall US infant mortality rate is around 5 deaths per 1,000 births, so this represents a very small increase relative to overall mortality. Another way to say it: 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. The main takeaway: if you are going to co-sleep, you should definitely not drink heavily 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 one can debate the merits of room-sharing at all, the AAP’s recommendation that it extend through the baby’s first year is problematic. Up to 90 percent of SIDS deaths occur in the first four months, so sleeping choices after four months are very unlikely to matter for SIDS. A 2017 study found that at four months, sleep was more consolidated for babies sleeping in their own room. At nine months, infants who slept alone slept longer — this effect was largest for those who moved to their own room by four months. Most notably, these differences were still present at age two and a half: children who slept alone by nine months slept forty-five minutes more per night than those still room-sharing at nine months. Sleep is crucial for child brain development; it is not just a selfish parental indulgence. It should also be said that if you plan to sleep-train your child, success is very unlikely while the child is sleeping in your room, and most people sleep better without a child in the room.
Across virtually all studies, the one thing that stands out as really, really risky is babies sharing a sofa with an adult. Death rates from this are twenty to sixty times higher than the baseline risk. An exhausted adult falls asleep holding an infant on a cushiony sofa, and it is easy for the infant to be smothered. The unfortunate thing is that in at least some of these sofa deaths, the parent was trying to avoid bed-sharing risks — hoping that if they sat up they would stay awake — and then fell asleep by accident. Even with the small risks of bed-sharing, you would 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, which is why the wearable blanket — a zipped-up bag you put your child in — is a reasonable recommendation to follow.
Chapter 7 — Organize Your Baby
Many aspects of scheduling will be kid-specific, and attempts to organize your baby are likely to meet with variation. But not everything varies. One thing that does not show as much variation is wake-up time. Even at around five or six months, the majority of children wake between six and eight in the morning. By age two, the range narrows to six-thirty to seven-thirty.
The other thing you realize with a 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. 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 United States, and 3 to 4 million were sickened. In 2016, zero children in the US died of measles, and there were an estimated eighty-six cases. The reason is simple: the development of a measles vaccine. Vaccinations are among the most significant public health triumphs of the past hundred years. Millions of lives worldwide have been saved by vaccines for diseases like whooping cough, measles, smallpox, and polio. The chicken pox vaccine has prevented a tremendous amount of discomfort and some deaths. The hepatitis B vaccine has reduced liver cancer. 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 — suggesting it is not lack of information getting in the way. The scientific consensus is extremely clear: vaccines are safe and effective, supported by a wide range of doctors, medical organizations, and government and non-government entities alike.
It is not entirely fair to say there are no risks at all. For many vaccines — all but the DTaP — there is a risk of allergic reaction, but this is extremely rare at about 0.22 per 100,000 vaccines, and treatable with Benadryl or, in extreme cases, an EpiPen. Fainting sometimes occurs after vaccination, mostly among adolescents, and does not have long-term consequences. There are three documented cases in the history of vaccination where the measles vaccine caused disease in immune-compromised children — categorized as a convincing link, but vanishingly rare and relevant only for children with immune issues. Similar considerations apply to immune-compromised children who receive the chicken pox vaccine. For healthy children, these are not risks you need to factor into your calculus.
One vaccine risk is more common and, while not serious, can be scary: the MMR vaccine is linked with febrile seizures, seizures that occur in infants or young children in association with high fever. About 2 to 3 percent of US children will have a febrile seizure before age five, most of which are not vaccine-associated. A number of studies find that these seizures are about twice as likely in the ten days or so after the MMR vaccine. They are actually more likely for children who get their first dose later, older than one year — which is a reason to vaccinate on time rather than delay.
On the question of vaccines and autism, the largest study includes 537,000 children — all children born in Denmark from 1991 to 1998. Researchers linked vaccination information to later diagnosis of autism or autism spectrum disorders and found no evidence that vaccinated children are more likely to be autistic; if anything, results suggest vaccinated children are less likely to be diagnosed with autism. There are many similar studies. One focuses specifically on children with an older sibling with autism — a higher-risk group — and again found no link with the MMR vaccine. There is no mechanism by which this would occur, and controlled studies in monkeys show no plausible relationship. Your child may well get a fever from a vaccine, and it is possible, though quite unlikely, that this fever could lead to a seizure. It is also possible, though 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?
Natural experiments in countries that changed parental-leave policies allow researchers to compare outcomes of children born under different policies without worrying about underlying differences across parents. By comparing children born during a six-month maternity leave policy to those born under a year-long policy, we can study the effects of leave on child outcomes without the confounding. 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 that one year of parental leave versus two years does not influence a child’s high school test scores or earnings in early adulthood.
For the impact of parents working when children are older, we are limited to correlational studies. When we look at schooling, test scores, and 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. 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 is not the decision that will make or break your child’s future success.
The financial math matters here too. Childcare is expensive, and most of it is paid in after-tax income, which means your income needs to be considerably more than the cost of childcare to break even. Consider a family with total income of $100,000, each parent making $50,000. After taxes, take-home pay is about $85,000. If both parents work and pay $1,500 a month for childcare, their disposable income after childcare is about $67,000. If one parent stays home, the family makes less — about $46,000 take-home — but pays nothing for childcare. The difference in take-home income is about half what it would be without children. This calculus gets more complicated if childcare is more expensive. A full-time nanny, especially with legally required taxes in an expensive area, can run $40,000 to $50,000 a year — completely wiping out one parent’s income.
Chapter 10 — Who Should Take Care of the Baby?
In economics, the advice is to “solve the tree” by working backward. First, decide what nanny you would want if you had to have a nanny. Then decide what day care you would want if you had to have day care. Then compare those two optimal options. Rather than comparing the full range of options across all categories, you face a very specific choice: your optimal day care setup versus your optimal nanny setup.
Research 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 researchers looked at behavior problems, there did not seem to be a relationship to day care quality in either direction. These results held through sixth grade: day care quality was associated with better vocabulary outcomes but not with behavior. Higher-quality day care is more expensive, of course, so a different set of kids are enrolled. The study adjusted extensively for family background, including home visits to evaluate parenting quality. Parenting matters a lot — way more than day care — but the day care results remained even after adjusting for observed parenting differences.
When evaluating caregivers, look at the basics: Is the adult available and interacting with the children, or are they on their phone? Do they have positive physical contact with the children — reinforcing good behavior with a hug, holding the baby? Then consider developmental stimulation: Does the adult read to the children? Talk to them? Respond when the baby makes a noise? Finally, there is behavior: how does the adult respond when children act out? Do they physically restrain the children, hit, or speak negatively? These would all be very bad signs.
More months in day care before eighteen months are associated with slightly lower cognitive scores by age four and a half, but more time in care after eighteen months is associated with higher cognitive outcomes. It could be that early on, one-on-one attention enhances language development, while at older ages, day care offers more exposure to letters, numbers, and social integration. Studies that combine both periods suggest that overall the effect is positive — kids in day care for more total time have better language and cognitive outcomes at four and a half. Kids in day care are more likely to get sick — mostly colds, fevers, and stomach flu — but these early exposures seem to confer some immunity, with fewer colds in early elementary school for those who were in day care longer as toddlers. Are kids in day care less attached to their mothers? No. Quality of parenting matters for attachment, but day care time makes no difference.
Two things come up again and again: first, parenting matters more than childcare type. Having books in your house and reading them to your kid will matter much more than what books they have at day care. Second, childcare quality matters much more than which type of childcare you have. A high-quality day care is likely better than a low-quality nanny, and vice versa. Beyond budget, consider convenience — Is there a day care close to home or work, or will you have to drive far out of your way? What are your options if your child gets sick? At-home care can still work with a sick kid, but day care cannot. 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. To the extent day care is worse, it seems to be worse early on — in the first year or eighteen months. To the extent it is better, that seems to be truer later. This could argue for a nanny or grandparent arrangement early on, followed by day care at a slightly older age.
Chapter 11 — Sleep Training
Good news: yes, sleep training works. There are many, many studies on this, employing a variety of related procedures, many of them randomized trials. A 2006 review covered nineteen studies of “Extinction” — 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 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 with longer follow-up — children who are sleep-trained sleep 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.
Most studies and virtually all sleep books recommend a bedtime routine as part of any sleep intervention. There is not much direct evidence — one review calls it a “common sense recommendation” — but it is generally included with all approaches. The idea is to have activities that signal bedtime: putting on pajamas, reading a book, singing a song, turning off the lights.
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 study reported that 70 percent of mothers met criteria for clinical depression at enrollment and only 10 percent after the intervention. 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 routine could have long-term positive effects.
A 2006 review of sleep training studies, which included thirteen different interventions, noted that adverse secondary effects were not identified in any of the studies. On the contrary, infants who participated in sleep interventions were found to be more secure, more predictable, less irritable, and to cry and fuss less following treatment. More recent studies draw the same conclusion — the babies are better rested, the parents are better rested, and everyone is in a better mood.
Ferber is a proponent of Graduated Extinction, while Weissbluth is more in favor of straight Extinction. There is evidence that all three methods work, with more evidence perhaps on the first two. There is relatively little evidence on which works best — some reports find Graduated Extinction is easier for parents and leads to more consistency; other studies find it prolongs crying. The only general principle is that consistency is key. Choosing a method and sticking with it increases success, so the most important consideration is likely what you think you can sustain.
Weissbluth suggests you can begin sleep training as early as eight or ten weeks. At this age, most babies cannot sleep through the night without eating — you should not expect your two-month-old to sleep for twelve hours. The goal at that age is to encourage the baby to fall asleep on their own at the start of the night and then only wake when hungry. A ten- or eleven-month-old, on the other hand, should be able to go through the night without eating, and training at that age focuses on both falling asleep independently and staying asleep. The goal of sleep training is not to deprive your child of basic needs like food and diaper changes — it is to encourage going to sleep independently once those needs are met.
Chapter 12 — Beyond the Boobs: Introducing Solid Food
In a landmark randomized study, children who were exposed to peanuts early were far less likely to be allergic at age five. In the group that did not get peanuts, 17 percent of children were allergic at five. In the group that received peanuts, only 3 percent were. Since the study was randomized, there was no reason other than peanut exposure for the difference, and it showed up in both high- and low-allergy-risk groups. Early exposure to peanuts is now the normal recommendation, especially for children at risk for an allergy.
Research also shows that babies whose mothers ate more of a particular food during pregnancy or breastfeeding were more likely to prefer that food — flavors pass through both the placenta and breast milk and affect whether children are receptive to new tastes. In a classic example, babies whose mothers consumed more carrot juice during pregnancy preferred carrot-flavored cereal over plain cereal, as measured by both consumption and facial expressions. Once children start eating solid foods, randomized evidence shows that repeated exposure to a food — giving kids pears every day for a week, say — increases their liking of it. This works for fruits and also for vegetables, even bitter ones.
Most kids become more picky around age two and then slowly grow out of it during their elementary school years, which can surprise parents whose eighteen-month-old ate everything. Kids are more likely to try foods with what researchers call “autonomy-supportive prompts” like “Try your hot dog” or “Prunes are like big raisins, so you might like them.” They are less likely to try things if parents use “coercive controlling prompts” like “If you finish your pasta, you can have ice cream” or “If you won’t eat, I’m taking away your iPad.” Putting it all together: 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 older, do not freak out if they do not eat as much as you expect. Keep offering new and varied foods. If they will not eat the new foods, do not replace them with something the child does like. And do not use threats or rewards to coerce eating.
The vast majority of allergies result from eight food types: milk, peanuts, eggs, soy, wheat, tree nuts, fish, and shellfish. Importantly, the research is about regular exposure, not just a one-time introduction — you need to actually keep giving your child the food. Go slowly: try a little bit at first, only one allergenic food in a given day, and see how they react. If nothing happens, give a little more, until you work up to a normal amount.
Soda is strongly discouraged for infants and children. Juice is more controversial, but generally young children should have formula, breast milk, or water once they start eating solid foods. Choking hazards — nuts, whole grapes, hard candies — are to be avoided. Grapes are fine in pieces, nuts are fine in nut-butter form. Cow’s milk is more complicated because it interacts with allergen issues. It is important to introduce milk-based foods like yogurt and cheese to avoid allergies, but milk itself as a primary drink is not recommended for infants — it is not a complete infant nutrition system, and infants who have it as their primary milk source are more likely to be iron-deficient. As an addition to oatmeal or cereal, it is not a problem.
The concern with honey is infant botulism — a serious disease in which a toxin interferes with neurological functions, including the infant’s ability to breathe. It is most common under six months, and while treatable with a very high success rate, the treatment requires the baby to be hooked up to a breathing machine for a few days. The toxin Clostridium botulinum is found in soil and in honey, and multiple case reports from the 1970s and 1980s of infant botulism associated with honey led to the recommendation against honey through the first year of life.
Your toddler or young child does not generally need a multivitamin. Even a child who seems like a very picky eater will be getting enough vitamins. The two possible exceptions are vitamin D and iron. Vitamin D is not present in high concentrations in breast milk, and since many of us live in houses in cold places rather than on the savanna, a lot of infants and children are considered deficient — potentially a quarter or more of white children, and higher among children of color, since darker skin lowers vitamin D absorption from the sun. What is less clear is whether this deficiency has much actual health impact. In two small randomized trials of supplementation, there were no impacts on bone growth or bone health, even though supplementation did increase vitamin D concentrations. This does not mean you should not supplement — rickets does occur in contexts with serious nutritional limits — but if you miss a day here or there, you should not panic.
Chapter 13 — Early Walking, Late Walking: Physical Milestones
Pediatricians focus on three key milestone checkpoints. At nine months, they look for rolling in both directions, sitting with support, motor symmetry, and grasping and transferring objects between hands. At eighteen months, they look for sitting, standing, and walking independently, as well as grasping and manipulating small objects. At thirty months, doctors look for subtle gross motor errors and any loss of previous skills, which can be a marker of progressive disease. The nine- and eighteen-month milestones are the most crucial; by thirty months, most major issues have already been identified.
There is enormous variation in when children hit physical milestones. Sitting without support ranges from 3.8 to 9.2 months. Standing with assistance ranges from 4.8 to 11.4 months. Crawling — which 5 percent of kids never do — ranges from 5.2 to 13.5 months. Walking with help ranges from 5.9 to 13.7 months. Standing alone ranges from 6.9 to 16.9 months. Walking alone ranges from 8.2 to 17.6 months. Variation within these wide normal ranges is not a cause for concern.
Kids younger than school age get an average of six to eight colds a year, most of them between September and April — about one a month. These colds last an average of fourteen days. A month is thirty days. So in the winter, your kid will have a cold roughly 50 percent of the time. Most colds end with a cough that can last additional weeks. Most are minor, though they increase the risk of ear infection and other prolonged bacterial infections like bronchitis or walking pneumonia. Most doctors will tell you to come in if you are concerned, if a fever lasts longer than a couple of days, or if your child gets worse after seeming to get better. Ear infections are the most common complication — about a quarter of kids will have one by age one, and 60 percent by age four. Colds do not respond to antibiotics since they are caused by a virus, and your doctor should not prescribe them. Globally, overuse of antibiotics is a public health problem because it contributes to antibiotic resistance. Even for your particular kid, antibiotics are not entirely risk-free — they can contribute to diarrhea, for example. The move toward prescribing antibiotics sparingly is a good thing.
Chapter 14 — Baby Einstein vs. the TV Habit
Research shows that children under two cannot learn much from screens. In one study testing whether babies could learn actions from video, twelve-month-olds learned nothing from the video demonstration, while older kids learned much less than from seeing a live person do it. In another study, researchers tried to maintain exposure of English-speaking nine- to twelve-month-olds to Mandarin language sounds through either a live person or a DVD. The live person worked well; the DVD did not. What does matter for language development at this age is books. The most significant predictor of both how many words children spoke and how fast their vocabularies grew was whether their parents read to them. Similar results hold for children up to age two.
Slightly older children can learn from television. Kids learn songs from movies and shows, and can pick up names of characters and basic plot elements. Lab research has shown that three- to five-year-olds are able to learn words from television. In the case of Sesame Street, there is actually good research suggesting that exposure increases school readiness in kids ages three to five. Early randomized trials found improvements in various measures of school readiness, including vocabulary, over a two-year period. A more recent study compared kids who got early access to the show 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.
One study reported that watching more TV under age three lowered test scores by a small amount — the equivalent of a couple of IQ points. However, watching TV at older ages did not seem to matter. When researchers compared kids who watched little TV before age three and then a lot between ages three and five to kids who watched little throughout, they found test scores to be no different — if anything, the kids who watched more TV later had slightly higher scores. Based on what is available, children under two cannot learn much from screens, children ages three to five can learn from screens, and the best evidence suggests that TV watching even at very young ages does not permanently 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
Parents often worry about whether their child is talking early or late relative to peers. There are standard tools to determine child vocabulary size, and there are metrics you can compare against — girls develop language faster than boys on average, though there is a lot of overlap across genders. The timing of language development does have some link with later outcomes like test scores and reading, but the predictive power for any individual child is weak. The key takeaway from the research is reassuring: early talking does not guarantee later success, even at age four, and late talkers mostly look like everyone else within a few years.
Chapter 16 — Potty Training: Stickers vs. M&M’s
There are two broad approaches to potty training, and they trade off differently depending on the child’s age. 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, which may make them easier to work with. 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 take advantage of their better ability to understand and control themselves.
On one side is a more goal-oriented approach, where you actively work toward toilet use on a defined timeline. On the other is a more laissez-faire approach, where you let the child lead with timing that works for them, looking for signs of readiness and encouraging toilet use when they become apparent. 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 adopt a more goal-oriented 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 a bit older. The child-led approach may take longer but may also be more pleasant for you. You will try anything — literally anything — to get your child to use the bathroom, but you cannot actually force them. Some kids respond to stickers, some to M&M’s, maybe some to meatballs. Potty training is really about what works for your family and your kid. Doctors generally do not worry about lack of nighttime dryness until a child is six years old.
Chapter 17 — Toddler Discipline
Before getting into evidence, it is worth stepping back and thinking about why we want to discipline our kids. The answer is the same as what we are trying to do with all our other parenting choices: raise happy, nice, productive adults. When a child refuses to clean up a mess and you discipline that behavior, it is not really that you want help cleaning up — it would be faster to do it yourself. It is that you are trying to teach them to be someone who takes responsibility for their messes, both the LEGO messes now and the inevitable non-LEGO messes of the future. This is the discipline-as-education philosophy: discipline is not the same as punishment. There is a punishment component, but it is in the service of raising better humans, not punishment for its own sake.
There are a number of evidence-based parenting interventions, including 1-2-3 Magic, the Incredible Years, Triple P — Positive Parenting Program — and others. Many schools, including those with children who have serious behavioral issues, use a similar program called Positive Behavior Interventions and Supports. For example, 1-2-3 Magic develops a system of counting in the face of disruptive behavior, and if three is reached, there is a defined consequence — a time-out, loss of a privilege, and so on. There is a strong emphasis on consistency: whatever system you use, use it every time, including in the grocery store. If you say no to something, you stick to no. If your kid asks for dessert and you say no, you cannot later say yes if they whine long enough — what do they learn from that? That whining sometimes works. And similarly, do not make threats you cannot carry out. One of the main tenets of these approaches is that discipline should be reserved for actual bad behavior, not for things that are merely annoying. Toddler discipline is, really, parental discipline.
Research has found 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. If hitting is the alternative, one of the evidence-based programs described above is probably worth a try.
Chapter 18 — Education
There is a large, well-established 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? Looking back at the day care research, more time in care after eighteen months 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. Many of the quality measures from the day care section apply here too: is the area safe, do the adults seem engaged, and so on.
The three preschool philosophies you will most commonly encounter are Montessori, Reggio Emilia, and Waldorf. Montessori focuses on a particular classroom structure and set of materials, with emphasis on fine motor skills. Children’s play is referred to as “works,” and even young children are exposed to letters, numbers, writing in sand, and counting blocks. Reggio Emilia-inspired schools put more emphasis on play, with typically little formal letter or number exposure at preschool ages — one school visited told me they explicitly do not spend any time on letters for the three- and four-year-old class and would not even display letter cards around the room, which seemed a little extreme. Waldorf schools have a heavy outdoor component, are largely play-based, focus on learning through play and art, and tend to include a domestic activity component — cooking, baking, gardening. All three methods have a structured day so kids know what to expect, and all acknowledge that young kids benefit from being able to explore in a safe environment and self-direct, to some extent, in what they do. We simply do not have a lot of concrete data to guide you on which philosophy is best. Further complicating both research and decision-making, it is possible — even likely — that the best type of preschool will vary by individual child.
Chapter 19 — Internal Politics
Research shows that parenthood hastens marital decline. Studies find that people who are happier before they have kids recover better, and that planned pregnancies are less impactful than unplanned ones. The effects are not enormously large — many people are still, on net, happy with their spouse. Just, slightly less.
Two specific factors play a role in this decline. The first is unequal chore allocation: women tend to do the bulk of household work even when 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 as well. 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 are cranky with your partner.
Some small-scale randomized interventions do show effectiveness. One is the “marriage checkup” — an annual meeting, possibly facilitated by a professional, to actually discuss your marriage. What do you feel is working? What is not? Are there particular areas of concern or unhappiness? These checkups seem to result in improvements in intimacy and marital satisfaction. 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. Broadly, these focus on communication and positive solutions to conflict.
Chapter 20 — Expansions
When researchers analyzed the effects of birth spacing on the older child, they found that test scores were higher if there was more space between siblings. This may reflect more parental time invested in reading or other skill development at young ages. The effects, though, were pretty small.
The bulk of the evidence suggests there are some small risks, both short and possibly long term, to very short birth intervals. Waiting until the first child is at least a year old to get pregnant again may be a good idea. It also may just 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. It makes sense to take parenting seriously and to want to make the best choices for your kid and for you. But there will be many times that you need to trust that if you are doing your best, that is all you can do. Being present and happy with your kids is more important than worrying about every small thing.
Use data where it is useful. Make the right decisions for your family. Do your best. And sometimes, just try not to think about it.