Photo: Matthew Gilson

An award-winning economist, University of Chicago professor, and new mom is declaring war on the traditional rules for pregnancy. In her forthcoming book, Expecting Better: Why the Conventional Pregnancy Wisdom Is Wrong — and What You Really Need to Know (out next week), Emily Oster combs through hundreds of medical studies to debunk many widely followed dictates: no alcohol, no caffeine, no changing the kitty litter. Her conclusions are startling, not least among them the revelation that there’s no good evidence to suggest that light drinking during pregnancy has any negative effect on the baby. (She concludes that woman should feel comfortable with one or two drinks a week during their first trimester, and up to one drink a day during the second and third.) She finds the evidence linking caffeine to miscarriage similarly flimsy, advising that one or two cups of coffee a day while pregnant are fine.

Oster advocates a more relaxed approach to pregnancy, and narrows down the huge restricted food list to a few items: rare meat and poultry, unwashed fruits and vegetables, raw-milk cheese, and deli turkey.

Expecting Better walks women through medical literature surrounding every stage of pregnancy, giving them data to make informed decisions about their own pregnancy. She spoke with the Cut about her conclusions, and why it’s so hard to find reliable studies on pregnancy.

For your book you looked at hundreds of studies that assess the effects of certain behaviors and medical procedures on pregnancy. It can be difficult to find reliable studies conducted on pregnant women, right?

Yeah. What you’d really like is to randomly tell some pregnant women to drink alcohol and some women not to — but there are some ethical problems with doing that, for reasons I’m sure I don’t have to explain. The biggest issue with the studies that do exist, then, is trying to separate correlation and causation. These days, we’re all told not to drink alcohol when we’re pregnant, so the kind of women who tend to drink alcohol while they’re pregnant tend to be different from women who don’t in a lot of dimensions. Yes, one of those dimensions is that they’re drinking alcohol, but they also tend to be poorer, not as well educated, and more likely to be single moms — things that we know are also risk factors for poor performance in schools. So the big problem here is when you then observe that the children of women who drank alcohol during pregnancy are now doing worse in school, it’s difficult to tell if that’s about the alcohol, or one of the other myriad problems that group has — the myriad ways in which they’re different from the group that didn’t drink. In the case of alcohol, many of the studies I relied on come from Europe, because there the prohibitions on alcohol during pregnancy are much more lax: They tell you to cut down, but it’s typically thought to be fine. So, you still have some women who drink and some women who don’t drink, but the two groups tend to be more similar, and so it’s easier to compare them and make conclusions.

You say part of the reason the “no drinks” rule has persisted for so long is that doctors tend to think that if a woman has one drink, it may be harder for her to stop — so therefore it’s better just to tell her not to drink at all, rather than explaining the risks.

I think there’s a general feeling that women should like rules. One of the reasons to have rules is so it’s like, “Well, you don’t have to think about this, because we’ve already thought about it for you.” And sometimes that’s okay, but it was frustrating when I did want to think more about it, and it was like, “Well, we’re not really equipped to help you with that.”

Another thing I will mention is that when I came to research what I call “the vices” — alcohol, caffeine, tobacco — there’s sort of a similar level of disgust with alcohol and tobacco. Like, don’t drink, don’t smoke. But in reality, it’s basically fine to have a glass of wine, but it’s really not okay to smoke; smoking is really bad. There’s plenty of evidence for that, and I go through a lot of it in the book. And in researching that I came to think that telling people that all of these things are terrible might lead them to say, Well, I’m already having a glass of wine, so I might as well smoke, whereas telling them, Look, here are the things you really need to focus on: It’s fine to have a glass of wine, it’s fine to have a cup of coffee, but do not use cigarettes. You get the same thing with the food prohibitions. There are like 5,000 things on the list, but really there are only six foods you should really avoid. I would say, “Why don’t you focus your time on not eating the things that are actually dangerous, rather than carrying around some six-page list restricting every food you might ever enjoy?”

How are the rules and guidelines for pregnant women established?

The official information is put out by the American Congress of Obstetricians and Gynecologists, and just like any sort of public-health rules, they tend to move slowly. If they’ve had a rule in place for a long time, a lot of new evidence has to come out before those guys are going to change their rules. That’s just the way those things happen. But even with that I noticed while I was researching that there are a lot of cases where the ACOG recommendation seemed to me basically correct, yet it’s not what’s happening in practice. So there’s both the issue that the general recommendations take a long time to change, but also that the way medicine is practiced isn’t always up to date.

In the book, you mention a number of instances where you found conventional wisdom and doctor’s recommendations for pregnant women to be overly cautious. Did you come across anything where the recommendations weren’t cautious enough?

I had always been told that you shouldn’t clean the litter box when you’re pregnant, because of your cat. And I think that is overblown — unless you have, like, three kittens in your house that are living outside and eating raw meat, this shouldn’t really be a significant source of concern. But gardening, which would have never occurred to me to worry about, is actually a more common source of this particular parasite than cat litter, probably because there are potentially more cats living in your yard than in your house. I’d never heard anything about gardening being dangerous during pregnancy, so it was a total surprise.

What do doctors think of your book?

I had a medical editor who read the book and I think she — well, I don’t know, but I think she liked it. I’m curious to see what the broader perception will be. I actually think that for many doctors there’s a sense in which having your patients be as informed as possible should be good, because you have a limited amount of time with your patient, and most doctors don’t have time to go through evidence like this, so having patients come in who are more informed and can really have an opinion is something I think many doctors will value.