Take Back Your Pregnancy
When she got pregnant, Emily Oster, associate professor of economics at the Booth School of Business at the University of Chicago, she found herself faced with the laundry list of rules that pregnant women have been handed for years regarding coffee, alcohol, soft cheese, deli meats, and so on. But when she looked at the studies behind the guidelines, she was surprised to see that most of them failed to make the distinction between causation and correlation.
In her article, Oster looked at several different issues that come up during pregnancy. For example, she looked at research regarding listeria, a bacteria that can cause miscarriage and stillbirth in pregnant women. Accordingly, pregnant women have been instructed to avoid deli meat, sushi, soft cheeses and other items. However, when she looked at what causes listeria, she found that since 1998, about 20% of listeria cases have been traced to the Mexican soft cheese queso fresco and 10% to sliced turkey.
"I concluded that avoiding queso fresco and deli turkey was a good idea, but in the end I didn't feel that it made sense even to exclude other deli meats," she wrote. "My best guess was that avoiding sliced ham would lower my risk of listeria from 1 in 8,333 to 1 in 8,255."
Oster's article focuses on two items that pregnant women are specifically discouraged from consuming - alcohol and coffee. Coffee consumption has been linked to miscarriage but coffee consumption generally is higher among older women, who are more likely to miscarry than younger women, independent of their coffee consumption.
Another reason that coffee consumption might be linked to miscarriage is related to nausea. Experiencing nausea frequently indicates that a pregnancy is going well but since coffee can cause upset stomach, women may not drink coffee if they're nauseous. The author herself is a coffee drinker but she skipped it when she felt nauseous in the beginning of her pregnancy.
Moreover, other sources of caffeine including tea and soda are less frequently associated with higher rates of miscarriage and are easier on the stomach, implying 1) that there's something specific about coffee drinkers as a population and 2) the nausea connection is important.