Sushi and Wine for Mothers-to-Be? New Book Suggests Pregnancy Rules Are Arbitrary

A new book questions the list of rules—from skipping the bar to avoiding deli meat—that most pregnant people are given during their first prenatal visit. Emily Oster, an economist, looks at the research and suggests many rules are based on caution rather than data. But many experts question her credentials.

A new book questions the list of rules—from skipping the bar to skipping the sushi bar—that most women are given during their first prenatal visit. Sushi and beet via Shutterstock

While she was pregnant with me, my mother was under doctor’s orders to drink one alcoholic beverage a day. It was the fall of 1972, and the fetus that would become yours truly wanted out, despite not being due for another two-and-a-half months. In order to “quiet the baby,” she was put on bed rest and told to drink. My mother says that she couldn’t stand the taste of alcohol at the time, so she masked it by having vodka in apple juice. Six weeks later—exactly one month early—I arrived, slightly pickled but with no apparent permanent damage. By the time I was pregnant, 33 years later, not only was alcohol during pregnancy demonized, but the list of things you could not eat, drink, or do for nine months was long and daunting, and the feeling that one small break of the rules could lead to a lifetime of guilt was enough to keep me in line.

A new book, however, suggests that many of these rules are based on an overabundance of caution rather than clear scientific evidence. Expecting Better: Why the Conventional Pregnancy Wisdom Is Wrong—and What You Really Need to Know was written by Emily Oster, a professor at the University of Chicago, who takes on today’s dos and don’ts of pregnancy, from avoiding deli meats to limiting caffeine intake. After carefully going through the existing research and recommendations from professional groups like the American Congress of Obstetricians and Gynecologists (ACOG), Oster provides her own conclusions for pregnant women, some of which are presented in a little box called “The Bottom Line.”

Here’s the wrinkle: Emily Oster is an economist. She has no medical or health-care background, just an understanding of statistics and a distaste for the seemingly arbitrary rules she was given during pregnancy. Many people are comparing her new book to the bestselling Freakonomics, which took an economic lens to numerous issues and suggested, among other controversial finding, that car seats for kids don’t really save lives and legalizing abortion reduced the crime rate. While some find her book to be a refreshing break from the standard pregnancy guides, which refuse to say that anything is not a risk, others think she has no business giving what appears to be medical advice.

Oster became pregnant in 2009 and says she expected to make decisions about her pregnancy the way she had been trained to do as an economist—by analyzing data. Instead, she was given a list of rules without explanation, and even when pressed her OB wouldn’t or couldn’t provide the thinking behind them. Conversations with friends revealed a lack of consistency in what doctors were saying, which further confused her. And guidebooks and websites were no help either. So Oster took matters into her own hands, pulling up the academic studies, working her way through the data, and reaching her own conclusions.

Here are some of the rules she takes on in the book along with the bottom line she reached.

Make Mine Decaf, Please. The current rule seems to be that pregnant people should limit their caffeine intake to the equivalent of two cups of coffee a day. While this might not seem like a huge hardship (seven years ago I was told only to have one), Oster wanted to see the research that showed caffeine was harmful or potentially harmful in large doses. Many of the studies she looked at questioned whether there was a link between caffeine consumption and miscarriage early in pregnancy. Some found no link, while others did—among them a 2008 study out of California that found a 25 percent miscarriage rate in women who drank more than two cups of coffee a day versus a 13 percent miscarriage rate in women who drank less, according to the book. Though this study seems to be where the rule stems from, Oster notes that there is one issue that the researchers do not seem to take into account: nausea. Early in the book, she examines research that confirms what everyone told me during the festival of dry heaving that was my second pregnancy: Feeling sick is great. It means a healthy pregnancy. It turns out they weren’t just blowing smoke; women with greater nausea have a lower chance of miscarriage. Oster argues that there is a relationship between nausea and coffee consumption during pregnancy. If you’re fighting the urge to puke every few minutes, you are probably not stopping at Starbucks for a latte. This could mean that the group of women who are not drinking coffee were self-selected and already had a lower chance of miscarriage. Though there is no data to prove this theory, Oster notes that studies of tea and soda, which are also caffeinated (though less so) but are much gentler on the stomach, have not found the same link to miscarriage. Her bottom line on caffeine is that almost every study finds two caffeinated beverages are fine and that much of the evidence says three to four cups wouldn’t do any damage either.

Sushi, Lunch Meat, and Fish, Oh My. Like many women, Oster was surprised to see so many foods on her new list of what not to eat. Her doctor told her to avoid sushi, deli meats, soft cheeses, and smoked fish and to limit her intake of fish in general. I remember grappling with this advice at an office holiday party. The pre-paid menu offered a steak (I hadn’t yet rediscovered red meat), a pasta dish with cilantro (which I despise), and a potato-crusted salmon that sounded pretty good. The problem was I had already eaten my two portions of fish for that week—my doctor’s advice had been to eat no deep-sea fish (tuna, swordfish, tile fish, or king fish) and to limit my intake all other fish to twice a week. I ordered the pasta without sauce. Oster says I probably didn’t have to take it so far. These eating rules encompass two concerns. The first is about food-borne illnesses, which is why pregnant women are told to stay away from raw meat, cured meat, lunch meat, and raw fish. Oster’s examination of the evidence basically says sushi, like raw eggs in a Caesar salad, is OK—you might get sick, but you won’t hurt your baby. Lunch meats, however, especially turkey, are probably worth avoiding because of the possibility of listeria, which has been found to cause miscarriage, preterm birth, and stillbirth in between 10 and 50 percent of pregnant women who become infected. Unfortunately, she also points out that recent outbreaks of listeria have been traced to celery, sprouts, and cantaloupe, and that in real life it’s hard to avoid completely. The other dangerous food-borne illness is toxoplasmosis, which comes from undercooked meats, dried and cured meats (like prosciutto), and unwashed vegetables. She advises washing raw veggies and avoiding raw and cured meats. (Later in the book, she debunks the idea that changing cat litter is risky for toxoplasmosis but does suggest that lots of gardening may increase exposure). The fish issue is about mercury and Omega-3 fatty acids. Mercury is bad for a developing brain (it’s been found to lower IQ), but Omega-3s are good (they’ve been found to raise IQ). Fish have both. The rule about limiting fish intake to twice a week is based on finding a balance between the two. Oster agrees this is important but thinks the answer lies in eating the right fish—those that are high in Omega-3s and low in mercury. In the book, she provides a chart, which divides fish choices into quadrants; canned tuna, grouper, and king mackerel are the worst, because they are high in mercury and low in Omega-3s, while catfish, pollock, sardines, and cod are the best.

You’re Not Really Eating for Two. One of the lowest points in my first pregnancy was when I met my OB’s partner for the very first time. (You’re supposed to rotate because you never know who is going to be on call when you go into labor.) Before even introducing herself, she looked at what the nurse wrote down and said, “How on earth did you gain seven pounds in four weeks?” I desperately wanted to lash out, “I’m pregnant, lady!” But instead I shrugged and sunk into the table with shame. A lot has been made about the idea of weight gain during pregnancy. Some research focuses on what is healthy for the pregnant person and some focuses on what is healthy for the fetus. Oster’s bottom line here seems very much based in common sense and actually ends with: “[C]hill out.” On the issue of the pregnant person’s weight, she says simply that what goes on must come off, and you know better than anyone else whether that will be hard or easy for you. As for the child, there is little evidence linking mother’s weight gain to the child’s weight later in life—so the issue is birth weight. As she puts it, in general the more weight you gain, the bigger your child will be at birth and vice versa. Babies with very high and very low birth weights can have health issues. She thinks it’s more worrisome to gain too little weight. But, mostly, she thinks we should all stop freaking out about how much weight we do or do not gain during pregnancy.

Oster goes on to address prenatal testing, what over-the-counter and prescription drugs are acceptable, epidurals during labor, and the benefits and risks of bed rest (she thinks it’s unadvisable in most cases). Her most controversial finding, however, has to do with alcohol consumption.

While nobody today would recommend a daily drink to prevent premature labor, there is debate about whether any amount of alcohol is OK at any point during pregnancy. As Oster explains, ethics prevents scientists from doing any kind of randomized controlled study on pregnant people. You can’t, for example, take a room full of similar women at similar stages of pregnancy and divide them into groups where one group binge drinks, one drinks a glass a day, and the other drinks none, and then compare their pregnancy outcomes. Instead you have to rely on pregnant women to report their drinking habits and compare those who do drink with those who don’t. The problem with this approach is that these women have other differences that can’t be ignored. Oster points to one well-cited study that found light drinking during pregnancy causes aggressive behavior in children. The problem with this study, however, is that the women who drank were also much more likely to use cocaine.

Though most of the advice for pregnant people ends with the phrase “No amount of alcohol has been proven safe,” Oster found this frustrating and not helpful when trying to decide whether to have a glass of wine or two. So again, she turned to the scientific research. The overwhelming evidence, she says, shows that light drinking is fine. To that end, her bottom lines include that women should be comfortable with one to two drinks a week in the first trimester and up to a drink a day in the second and third trimesters. She does point out that speed matters and that seven drinks a week does not mean that it’s OK to have them all at once.

This advice has drawn the ire of many in the medical community and those who have been affected by fetal alcohol syndrome (FAS). Dr. Todd Ochs of Ravenswood Pediatrics of Chicago explained to the Chicago Tribune that any alcohol that is not processed by the woman’s liver travels through the placenta into the fetus’ bloodstream. He added, “If she is a slow metabolizer, the fetal brain is bathed in a toxin. How can that be good … why would a mother do something to put her baby at risk?” A comment on an article Oster wrote for The Atlantic echoed this sentiment:

I am the foster-adoptive mother of two beautiful girls who are on the fetal alcohol spectrum, one with FAS and the other with FAE [fetal alcohol exposure]. I am also a researcher in educational psychology and special education, so I am quite familiar with the FAS literature. While I agree with Oster that the literature, by and large, does not support the contention that modest alcohol consumption during pregnancy is likely to promote FASDs or other disorders, as a mother of two girls on the fetal alcohol spectrum, I speak with authority when I say that encouraging women to indulge in alcohol during pregnancy simply isn’t worth the risk.

Others take their disapproval of Oster further, saying that she simply has no business giving out what seems an awful lot like medical advice. For her article in the Daily Beast, which is critical of Oster’s advice, Jacoba Urist spoke with a number of medical professionals. One said that she can’t imagine a doctor ever trying to evaluate economic data and give policy suggestions on housing or the financial sector. Though Urist admits Oster is no Jenny McCarthy, she believes her approach is similar to the one that The View host used when writing her book and concluding that vaccines caused her son’s autism. Urist focused on Oster’s suggestion that mothers-to-be dive into the research themselves and concludes that “telling parents with no scientific training to do it yourself can have dangerous consequences.”

When I read Oster’s book, I focused not on the suggestion to find my own information—perhaps because I am not pregnant and never plan to be again—but instead on what she found in her statistical analysis of the data. I find data, and the way it can be used to support different points of view, fascinating. And I found her explanation of it well-written and refreshingly easy to understand. I gave up on pregnancy guides by my second month of pregnancy, because I found they were either difficult to follow, condescending, or panic-inducing (and some were all three). Going to the Internet for information was even more of a crapshoot; half the time I ended up with the opinion of one parent who knew less than me. In fact, a few weeks ago, when I wrote about a new prenatal test for Rewire, I scoured the Internet for information. So much of what I found was confusing and poorly explained, and the one nugget I really needed was buried under a lot of repetitive information. I told my editor that I had decided I needed to rewrite the Internet. All of it.

I definitely would have found Oster’s book helpful in writing that article and do wish it had been around during my pregnancies. That said, I’m not sure how much I would have relied on her advice to guide my actual behavior. Much of her frustration came, at least by my read of it, from having an unhelpful OB who didn’t answer her questions. While Oster said that her OB would not explain to her why amniocentesis was recommended only after age 35, my OB told me exactly why: That’s the age at which the risk of having a baby with Down syndrome becomes greater than the risk of having a miscarriage from an amnio. She also told me that the miscarriage risk from amnios included those that happened with inexperienced doctors and rural hospitals with outdated equipment. The rates at the practice I would be going to were much better. And during my very first visit, my doctor said I could eat sushi if I wanted to, told me to keep my appointment with my colorist (hair dye is often cited as a no-no), and assured me that a glass of wine now and then wasn’t such a big deal.

Now that I think of it, maybe if Professor Oster had gone to see my doctor—with her sensible advice and willingness to share the data behind it instead of whoever she did see—there would be no book.