Parenting by the Numbers

She cut me off, saying, “There’s a book you need to read.” The book was by Emily Oster, an economist at Brown University who studies health care. (Her conclusion: a glass of wine a day in the second or third trimester wasn’t a problem, and she could keep drinking coffee guilt-free.)Oster’s research expanded into her 2013 book, “Expecting Better,” which became a hit among pregnant women—at least among the subset of pregnant women with the time and resources to devote to issues like caffeine dosage and sushi intake. The president of the American College of Obstetricians and Gynecologists said, on Boston’s NPR station, that Oster’s advice was wrong: “We need to err on the side of caution, and the side of caution says that we have not been able to identify any amount of alcohol that is absolutely safe in pregnancy.” But Oster’s fans were undeterred. Amy Schumer called Oster “the non-judgmental girlfriend holding our hand and guiding us through pregnancy and motherhood.”Last month, Oster published a sequel, “Cribsheet,” subtitled “A Data-Driven Guide to Better, More Relaxed Parenting, from Birth to Preschool.” It takes on subjects like cold season, nap schedules, and potty training. Levitt, who has six children, including two who are younger than three, told me that Oster’s first book “is the bible of my circle.” At a time when pregnancy and child rearing have become polarized and moralized—natural births, water births, orgasmic births?—it can be refreshing to hear from someone who sticks to the numbers. In a chapter in “Cribsheet” about staying at home versus working, she writes that, while she loves her children, “the marginal value of time with my kids declines fast.” In a section on milk oversupply during breast-feeding, she mentions gua-sha therapy, a skin-scraping treatment, and adds, “Gwyneth Paltrow swears by this, so take what you will from that.”From the books, I also knew a good deal about Oster’s family. As a child in the nineteen-eighties, Oster said, “we were the only people who ordered groceries from the grocery store.” When young Emily asked her mother, “Why don’t we ever go to the store, like regular people?,” her mother told her, “Because my time is very valuable. I have a high opportunity cost.” Naturally, Oster recalled, “I was, like, Oh, O.K. That makes sense.”Oster was a precocious child. Oster ducked into his closet, swiftly selecting clothes.Addressing me, Finn asked, “Would you like to listen to the book that Mom’s going to read to me?”“What do you want me to read?” Oster asked. “These are on backward.” The Stormtrooper logo was on the rear, so he’d turned them around.“It’s a terrible underwear design,” Oster said.We talked about their weekend plans, and about a Japanese restaurant where they’d recently eaten.“You sit on a tatami mat,” Penelope told me. She went on, “Now that I’m done with Japan, I’m studying family.”Oster asked, “Are you going to write about our family?”Penelope was interrupted by Finn, who shouted, “More fizzy water!”“Please,” Oster said, and refilled his glass.“Cribsheet” is different from Oster’s first book, in part because pregnancy and parenting are different. “When you have a kid, it’s like someone is shooting you in the face with a fire hose,” Oster said. She dug into the data on such topics as sleep and childcare, asking, “What, ideally, should I have done?” The answer wasn’t always clear.For one thing, there isn’t much data on the nonmedical aspects of child rearing, such as the effects of screen time on kids. Yes, it’s fine,” Oster said, by way of example. By the nineteen-seventies, after the baby-formula industry aggressively marketed its product to doctors, breast-feeding had declined precipitously in the U.S. It was revived in the nineteen-eighties, thanks to large-scale public-health campaigns, and later to studies showing such health benefits as improved metabolism and higher I.Q. If you’ve been pregnant in the past forty years, you’ve no doubt been on the receiving end of these campaigns—from the poster in the doctor’s office announcing “Breast Is Best!” to the Instagram influencer doing yoga while a baby suckles peacefully at her nipple. I just want to be able to tell my wife it’s not so terrible if this doesn’t work,’ ” Oster said.After reviewing the literature, Oster believes that the health benefits of breast-feeding are real, but that they have been oversold. Important, but, as Oster told me, “if it doesn’t work, the parents should say, ‘Well, maybe my kid will have more difficulty pooping for a few months.’ Not ‘There go five I.Q. points!’ ”Another question that people often ask new mothers: “Is your baby a good sleeper?” Sleep is a fraught topic, in part because it’s stalked by the world’s scariest acronym: SIDS, or sudden infant-death syndrome. In other words, Oster said, “a reasonable person could make that choice,” especially if it’s helping the entire family sleep.Economics is a science of decision-making. “In the first book, there’s a central tension between people and the medical establishment,” Oster told me. “My son is twenty months old, and I can’t figure out how to stop breast-feeding him,” she said.“There isn’t much data on that,” Oster replied, apologetically. “That’s the really scary part of having a person like Oster, who is not an epidemiologist, distilling this information to the lay public,” Feldman-Winter told me. She was surprised to find that, as she writes in the book, “they just work.” A number of large randomized controlled trials have shown that, after parents are taught the techniques, they report that their children are more compliant, and that they themselves are less stressed—even years after the program has ended.Oster has started using 1-2-3 Magic with her kids. “You have to be consistent,” Oster said. Oster now finds herself brainstorming punishments that a four-year-old will find “devastating.” Lately, she said, she’s been having success with “If you don’t stop doing that, I’m going to take away your lunch cookie.”Talking about this subject, I was reminded of a recurring episode in “Narratives from the Crib.” It takes place at the beginning of each tape, before Baby Emily’s dad puts her to bed.