Pregnancy! A time of wonder and anticipation. And paranoia. First comes the visit to your doctor, where you receive the (hopefully) happy news. Then comes the Talk, which goes something like: “Remember to take it easy for the next nine months. Pamper yourself. Get lots of sleep. And don’t eat any deli meats, or you could murder your baby.”

O.K., this might not be exactly what the doctor says, but it’s what many women hear. Daily life takes on a frightening new dimension. Is there toxoplasmosis on the cat’s butt? Is the hair salon full of poisonous fumes? Complicating things is the gap between the official recommendations and what people actually do. The handout says stick to “one small cup” of coffee and stay away from alcohol. But we all know that the coffee thing is B.S., and that it’s perfectly fine to have a glass of wine, because . . . they do it in France, right? What about that trending Times article, “Eating Nuts During Pregnancy Tied to Brain Benefits in Baby”? Or the fact that Kourtney Kardashian avoided microwaves after she had a baby?

Navigating this gantlet, when I was pregnant, I called a friend who had recently given birth. 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. In her day job, she pores over medical journals and government data sets for insights into how we treat diseases such as Huntington’s, diabetes, and H.I.V./AIDS. In 2010, Oster got pregnant. Confronted with the usual mixed messages—her doctor told her that a glass of wine was “probably O.K.”—she went home, logged in to PubMed, a database of medical literature, and downloaded every study on alcohol and caffeine going back to the nineteen-eighties. She then spent several days performing a personal meta-analysis: evaluating the merits of the studies, throwing out the weak ones, and making an assessment of the risks. (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. In the book, Oster recounts the choices that she faced during her pregnancy and tackles such topics as prohibited foods, weight gain, and C-sections, frequently dismantling the received wisdom. Flatteringly, she addresses her reader as a peer. She doesn’t issue opaque decrees, with the implicit condescension of “Trust me, I’m an expert.” She doesn’t slip into cutesy jargon, like the pun-prone authors of the latest edition of “What to Expect When You’re Expecting,” who call pregnant women “Mama” and suggest that you “start every morning with a bump selfie.” Instead, she takes the reader on a tour of the scientific literature, even describing the methodology of specific studies to show how she made each decision. Lauren Kay, the executive editor of the pregnancy and parenting Web site the Bump, explained Oster’s appeal to me in an e-mail: “The whole tone of the book is very pro-Mom, putting the power back in the hands of the pregnant woman. I read it when I was pregnant with my first child, and it left me feeling empowered to ask my OB why or why not. It also reminded me that I was part of the equation, too.”

Despite the plaudits, the book didn’t go over well with many public-health officials, who disagreed especially vehemently with Oster’s conclusions about alcohol. 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. As the mother of a sixteen-month-old, I had a host of burning questions: Will she ever willingly wear clothes? Is it wrong to buy those little kids’ leashes? Why does she put her finger in other babies’ mouths and say, “Bite”?

Parenting experts have been around for as long as there have been anxious parents. They have channelled the fears and the aspirations of their times. Eighteenth-century parents adopted Jean-Jacques Rousseau’s ideas about “natural” parenting—cold air is good for a child!—even though he’d left all five of his children at a foundling hospital. Dr. Spock, who had trained in psychoanalysis, gave parenting advice a Freudian spin, and his mantra—“Trust yourself. You know more than you think you do”—soothed addled Cold War parents.

It makes sense that our parenting expert du jour is a data wonk. In some ways, data are to today’s parents what psychoanalysis was to the postwar generation: a hoped-for savior. We try to make sense of a chaotic world by reading Nate Silver’s political forecasts and wearing devices that count our steps. At the same time, Big Data is increasingly sinister. If you’ve been pregnant lately, you’ve undoubtedly had the eerie experience of seeing baby-related ads popping up online before you’ve shared the news with anyone. The information age has turned out to be a breeding ground for misinformation, with “Moneyball” giving way to Twitter bots, viral pseudoscience, and dubious Facebook news feeds.

Oster is here to help you navigate this glut. As a pop-economist, she follows in the tradition of Steven Levitt, of “Freakonomics” fame. 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. “Economists focus on how the world is,” Levitt told me. “A lot of parenting advice is focussed on how the world should be in someone’s mind.”

What did I want from Oster’s books? Until recently, most of life’s outcomes seemed within my control. If I exercised, I could get in shape. (Not that I ever did.) If I worked hard at school, and then at my job, I could earn good grades and promotions. But becoming a parent was different. No matter how many pregnancy apps I downloaded, I couldn’t control when I would get pregnant, or if it would go well. And, after the baby arrived, I seemed to be stuck in crisis mode. The data seemed like a way to get back, if not power, then at least a sense of mastery.

Oster now has two children, Penelope and Finn, who are eight and four. She spends most of her days in her office at Brown, where she is currently researching methodological problems with data on health trends (vitamins, superfoods). Given the subject matter of her books, I thought it best to see her in the domestic sphere. I arrived at her home, in Providence, Rhode Island, at 6:30 a.m. It was still dark outside. Oster was standing at her kitchen counter in working-mom attire: a black business skirt and stockings, with a zip-up hoodie over her blouse to protect it from grubby hands. The place was neat but minimally furnished—an indication, to me, that she wasn’t especially interested in interior decorating. But I knew from her books that she likes to sew, and there were two plates of attractive muffins on the counter. She’d gotten up at 5 a.m. to bake.