Cribsheet: A Data-Driven Guide to Better, More Relaxed Parenting, from Birth to Preschool (The ParentData Book 2)

by Emily Oster

As a parent, you want nothing more than to do the right thing for your children, to make the best choices for them. At the same time, it can be impossible to know what those best choices are. Things crop up that you never thought about—even with a second kid, probably even with a fifth kid. The world, and your child, surprise you all the time. It is hard not to second-guess yourself, even on the small things.

it illustrates what will be one of the great themes of your parenting life: you have way less control than you think you do.

you do have choices, even if not control, and these choices are important. The problem is that the atmosphere around parenting rarely frames these choices in a way that gives parents autonomy.

Most of us are parenting later than our parents did; we’ve been functional adults a lot longer than any previous generation of new parents. That’s not just a neat demographic fact. It means we’re used to autonomy, and thanks to technology, we are used to having pretty much limitless information in our decision-making. We’d like to approach parenting the same way, but the sheer number of decisions causes information overload. Especially early on, every day seems to have another challenge, and when you look for advice, everyone says something different. And, frankly, they all seem like experts relative to you. It’s daunting even before you factor in your depleted postpartum state and the tiny new resident of your home who won’t latch onto your breast, sleep, or stop screaming. Take a deep breath.

And on top of these questions is the endless worrying, “Is my kid normal?” When your baby is just a few weeks old, “normal” is whether they are peeing enough, crying too much, gaining enough weight. Then it’s how much they sleep, whether they roll over, whether they smile. Then do they crawl, do they walk, when do they run? And can they talk? Do they say enough different words? How can we get the answers to these questions? How do we know the “right” way to parent? Does such a thing even exist? Your pediatrician will be helpful, but they tend to (correctly) focus on areas of actual medical concern.

But this wasn’t the whole story, since this didn’t take into account the value of my time. Or, as economists like to say, the “opportunity cost.” I was spending time prepping food—fifteen, thirty minutes a day, usually early in the morning. I could have spent it doing something else (say, writing my first book more quickly, or writing more papers). This time had real value, and we couldn’t ignore it in the calculation. Once we factored this in, the meal kit seemed like a great deal, and even take-out started to sound appealing. The dollar difference was small, and the cost of my time more than made up for it. Cooking two dinners, though, looked a lot worse: more time cooking, not less.

Too often we focus on the benefits at the expense of thinking about the costs. But benefits can be overstated, and costs can be profound.

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.

There is reassurance in seeing the numbers for yourself. People may tell you it’s fine to let your child “cry it out” to fall asleep, but you’ll probably feel better doing it once you’ve seen the data shows this to be true.

It is hard to overstate how different things are in the moments before and after the baby, especially when that baby is your first child.

The first few hours or days in the hospital, and then the first weeks at home, can have a kind of hazy quality. (This might be the sleep deprivation.) You’re not seeing many other people (unless you’re hosting unwelcome family members) or leaving the house much, you’re not sleeping or eating enough, and there is all of a sudden a demanding person who wasn’t there before. A WHOLE PERSON. Someone who will one day drive a car and have a job and tell you they hate you for ruining their life for not letting them go to a coed sleepover that everyone else is going to.

The days right after giving birth are a confusing time, and can be made more so because of the often conflicting advice you will receive from your care providers, your family and friends, and the online world.

Many new parents are not expecting the tremendous focus doctors and hospital staff place on infant weight gain or loss.

nearly all infants lose weight after birth, and those who are breastfed lose even more. The mechanisms for this are well understood. In the womb, your baby is getting nutrients and absorbing calories through the umbilical cord. Once the baby is out, he has to figure out how to eat. It is complicated (for both of you), and in the first few days, you won’t yet have a lot of milk. Colostrum may or may not be the magical substance that lactation consultants fantasize about, but there isn’t much of it (especially with your first baby). The fact that this weight loss is expected means you want to be careful about this issue, but you also want to make sure not to overreact to the design of the system.

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.

Jaundice is a condition in which the liver is unable to fully process bilirubin, a by-product of breaking down red blood cells. Everyone, baby or not, relies on their liver to break these down, and in principle anyone can be jaundiced. Infants are at higher risk for this just after birth for a few reasons. There are more blood cells being broken down shortly after birth, increasing the load of bilirubin presented to the liver. At birth, the liver remains immature and therefore has difficulty excreting this higher load into the gut. Finally, in the first few days of life, babies are not eating a lot, so the bilirubin hangs out in the gut where it gets reabsorbed back into the bloodstream.

Severe untreated jaundice can lead to a condition called kernicterus, a form of long-term brain damage.

Jaundice is also very common, especially in breastfed newborns: about 50 percent of newborns will have this condition to some degree. It’s important to note that the brain injury effects are not on a continuum: at low or moderate concentrations, bilirubin doesn’t cross the blood–brain barrier and is therefore not damaging.

The key decision for the doctor is whether bilirubin levels are high enough for “phototherapy”—aka a blue light box. This type of treatment typically occurs in the hospital, and involves having the infant spend time naked (other than a diaper and an eye covering) in a bassinet that is emitting blue fluorescent light. The light breaks down the bilirubin into other substances that are passed out of the body in the baby’s urine.

Swaddling is thought to improve sleep and decrease crying. If true, these are very good reasons to swaddle, since the main things babies seem to like to do are cry and not sleep. And fortunately, this turns out not to be very difficult to study, since sleep is a very short-term outcome. Researchers can look at the same baby swaddled and unswaddled. This avoids a lot of our concerns about different parents doing different things with their babies.

The study strongly supported the value of swaddling for sleep. While swaddled, the babies slept longer overall, with more time spent in REM sleep. This paper also identified the mechanism: swaddling improves sleep because it limits arousals.3 Swaddled babies are equally likely to have the first stage in arousal—measured with baby “sighs”—but are less likely to move from this to the second stage (“startles”) or the third (“fully awake”). Something about the swaddle discourages these second and third stages. These effects are big. The study found that when babies were not swaddled, a sigh turned into a startle 50 percent of the time. When they were swaddled, this occurred only 20 percent of the time. This type of laboratory evidence is confirmed by observational data and descriptive studies.

But you basically cannot defeat a crying baby with hard work. There may be some things that improve this in the moment, but babies cry—some of them cry a lot—and there is often really nothing you can do. In a sense, the most important thing to understand is that you are not alone and that your baby is not broken.

It is also important to say that this is “self-limiting”: colic will go away, typically around three months. Not all at once, but things will start to improve.

Regardless of what you do, your baby will still cry, sometimes for what seems to be no reason at all. It may not feel like it at the time, but this will go away, and you’ll more or less forget about it as your child ages (this is presumably why people are willing to have a second child). Older babies do cry, but mostly for reasons you can understand or at least identify. Management of your own stress levels is at least as important as managing the baby’s crying.

As the baby gets a bit older, keeping track of when the baby eats may help form a schedule. But in the first weeks, a feeding schedule is a bit of a pipe dream. 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.

There is a broad theory called the hygiene hypothesis, which states (I am paraphrasing here) that the increase in occurrences of allergies and other autoimmune illnesses over time is a result of decreased germ exposure in childhood, and that exposure to more microbes and germs as a child can help their immune system properly identify and not overreact to perceived pathogens.13 While we don’t have conclusive proof that this is true, there is some evidence backing the theory in the form of laboratory studies of particular cells and comparisons across cultures in rates of various diseases. 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.

Once your baby is over three months, and especially after they’ve had the first set of vaccines, treatment of a fever is closer to what you’d expect with an older child—basically, give them some Tylenol, keep them hydrated, and wait for it to go away. At this point, the downside of germ exposure is simply a sick kid, not a cascade of invasive testing.

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.

Collecting data on your baby is fun! But not necessary or especially useful.

You can bleed too much—maternal hemorrhage is a possible postbirth complication. Since you know you should bleed some, it can be hard to know how much is too much. If you’re not sure, ask. If you see a clot and think, Is that the size of a fist, or just a bit smaller?, don’t wait around measuring it for yourself—buzz the nurse. The passing of clots will die down after a couple of days, but you’ll keep bleeding—first like a heavy period, then a lighter period—for weeks. Once you’re home, the bleeding should decrease over time. If, all of a sudden, you start bleeding a lot again, especially if the blood is bright red, call your doctor immediately.

After a caesarean, doctors generally want you to either poop or at least pass some gas before you leave the hospital; this is to ensure that you can have a bowel movement after what is basically major abdominal surgery. It is not unusual for it to take several days for this to happen. In service of this, you’ll get stool softeners. In the absence of vaginal trauma, the actual act may not be that uncomfortable. Sitting down, however, can be painful due to your incision.

With both vaginal and caesarean deliveries, there are other common, mostly minor, lingering consequences. Hemorrhoids, for example. Also, incontinence. Many women find that after childbirth, they pee a bit when they cough or laugh, or seemingly for no reason. This, like other things, will improve over time.

In the case of exercise, there is relatively little concrete evidence on when it is okay to start. The American College of Obstetricians and Gynecologists says that it is safe to resume exercise “within a few days” after a normal vaginal delivery. This isn’t to say you will be running interval workouts a week later, but some walking may be feasible. They caution, though, that this will be different if you’ve had a caesarean or significant vaginal tearing. In the case of a caesarean, the standard recommendations include some walking within the first two weeks, introducing the possibility of abdominal curls or other related exercises by week 3 and a resumption of “normal” activities by around week 6.3 Again, healing rates differ from woman to woman, so this is really just an average.

Nearly all people—including elite athletes, but also recreational athletes and those of us who just walk or run for exercise—should be able to resume pre-pregnancy activity levels by six weeks postpartum and some modified version before that.

Even if you are breastfeeding and just had a baby three weeks ago, you can get pregnant.

Looking at the data—which, in this case, may not be so helpful, since really the question is when you want to do it—most couples have resumed at least some sexual activity by eight weeks postpartum. For those with an uncomplicated vaginal delivery, the average is about five weeks, versus six weeks for caesarean and seven for those with significant vaginal tearing.4 Having said this, it takes an average of about a year to get back to pre-pregnancy sex frequency, and many people never return to having quite as much sex as they did before.

Women (or men) who have less social support, who experience difficult life events around this time, or whose baby has medical or other problems are more likely to be depressed. And the baby itself can also play a role; people with babies who are poor sleepers are at greater risk for depression, almost certainly due to the fact that they, in turn, get less sleep.

There are many issues in the pre-pregnancy, pregnancy, and post-pregnancy world that we do not talk about enough. When I was writing about pregnancy, the thing that struck me in this category was miscarriage. So many women have had miscarriages, yet they are rarely talked about—until you have one and then it turns out many women you know have also miscarried. Postpartum mental and physical health have the same pattern.

What we can say is that the data doesn’t support the claim of a reduction in respiratory infections as a result of breastfeeding. Given these findings, why do we continue to see the “evidence-based” claim that breastfeeding reduces colds and ear infections? The main reason is there are many observational studies—which compare kids who are breastfed with those who are not, but not where breastfeeding is randomly varied—that do show that breastfeeding affects these illnesses. An especially large set of studies argues for an effect of breastfeeding on ear infections.10

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.

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.

The pressure on moms to breastfeed can be immense. The rhetoric makes it seem like this is the most important thing you can—and need—to do to set your child up for success. Breastfeeding is magic! Milk is liquid gold! This just isn’t right. Yes, if you want to breastfeed, great! But while there are some short-term benefits for your baby, if you don’t want to nurse, or if it doesn’t work out, it’s not a tragedy for your baby, or for you. It is almost certainly worse if you spend a year sitting around feeling bad about not nursing.

I can perhaps be accused of armchair psychology here, but these struggles seem particularly acute because trying harder—something that usually breeds success—doesn’t always work with breastfeeding. You worked hard to get a job, or to get into college—even to get pregnant—and you were successful! But introduce a new person, and some further constraints of biology, and all bets are off. You may have to accept, as I did, that no matter how hard you try, you will not make quite enough milk.

First, there is some randomized evidence on the success of skin-to-skin contact at improving breastfeeding success rates.

Second, there is some (more limited) evidence that breastfeeding support—by a doctor, or by a nurse or lactation consultant—can increase likelihood of breastfeeding initiation and continuation.

Despite the warnings, there is simply no evidence that the use of pacifiers impacts breastfeeding success. This has been shown by more than one randomized trial,14 including trials that start infants on a pacifier at birth.

It’s a good lesson in how things change; generally, the recommendation now is to nurse on demand, at least early on, since this establishes a plentiful milk supply. Schedules, to the extent we get them, come later.

When your baby is first born, you’ll produce a small amount of colostrum, an antibody-rich substance. (You’ll actually start producing this in late pregnancy.) Over the first few days, as you nurse, your body will eventually (in theory) switch over from producing colostrum to producing milk in more copious amounts. The expectation is that this switch to more full milk production—scientifically termed lactogenesis II, and sometimes referred to as your milk “coming in”—will occur within the first seventy-two hours after you’ve given birth. If this doesn’t happen, you will be deemed as having “delayed lactogenesis.”

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.26 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.

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.29 And this is in a kind of “worst-case scenario.” This paper cautions that drinking four drinks quickly will impair your ability to parent and is not healthy, so it should be avoided, but the issue isn’t alcohol in your breast milk. Therefore, there is no need to pump and dump. The milk has the same alcohol concentration as your blood. As that goes down, so does the milk alcohol level. It isn’t stored in the milk.