Too much caffeine during pregnancy could increase the risk of miscarriage, which is a pregnancy loss before twenty weeks of gestation, according to a new study being published in the American Journal of Obstetrics and Gynecology). But if you pick up the most recent issue of the journal _Epidemiology_, you will find a study stating that there is no link between miscarriage and caffeine consumption -- so what should a woman contemplating pregnancy believe?
The study in the American Journal of Obstetrics and Gynecology reported that women who consumed caffeine but had less than 200 milligrams of caffeine -- about two cups of coffee or five cans of soda per day (a "tall" Starbucks coffee has more than 200 milligrams of caffeine) -- were 40% more likely to have a miscarriage than women who did not consume caffeinated drinks. Those who consumed 200 milligrams or more of caffeine had an almost doubled rate of miscarriage compared to those who consumed no caffeine. The study was based on self-reported one-time interviews of 1,063 women who were a median of ten weeks pregnant, some of them having already miscarried.
Morning sickness complicates such analyses. Many scientists postulate that caffeine only seems to increase miscarriage risk because women with morning sickness, who are more likely to carry a pregnancy to term, tend to avoid caffeinated beverages. The study claimed to control for morning sickness, but so did the study in Epidemiology that says there is no link between moderate caffeine consumption and miscarriage -- which brings pregnant women back to square one. The second study included 2,047 women who drank less than 200 milligrams per day of caffeine while pregnant.
Some risks to a healthy pregnancy are well known and understood, such as smoking or not getting enough folic acid, while some are not so well understood -- such as caffeine intake. Overall, there is no concrete evidence that having caffeine in moderate amounts increases risk of miscarriage.
Pregnancy can often be a time of worry for expectant mothers who are trying to balance their normal dietary routine with the requirements of their baby. Despite decades of study on the caffeine-miscarriage association, there does not seem to be any clearer advice on the issue than there has been in the past, based on recent studies. Pregnant women should monitor their caffeine intake to ensure it's on the low side but focus on avoiding the better-documented risks to their pregnancy.
Krystal Wilson is a research associate at the American Council on Science and Health (ACSH.org, HealthFactsAndFears.com).