Caffeine may pose miscarriage risk

A new study is suggesting that pregnant women who consume over 200 milligrams of caffeine per day are at increased risk of miscarriage:

Dr. Li’s study included 1,063 pregnant women who were interviewed once about their caffeine intake. At the time of the interview, their median length of pregnancy was 71 days. But 102 had already miscarried — not surprising, because most miscarriages occur very early in pregnancy. Later, 70 more women miscarried, for an overall miscarriage rate of 16 percent for the group — a typical rate.

Of 264 women who said they used no caffeine, 12.5 percent had miscarriages. But the miscarriage rate was 24.5 percent in the 164 women who consumed 200 milligrams or more per day. The increased risk was associated with caffeine itself and not with other known risk factors like the mother’s age or smoking habits, the researchers said.

The general advice that pregnant women should avoid caffeine is not particularly new, although this study seems to be the most current and most specific. But contrast this with another recent study we talked about last year:

At the beginning of this year, a Danish study published findings on this subject: 1,200 women were surveyed, which is more than double the sample of the next largest study. The adjustments for confounding factors were comprehensive, and the conclusion was that no significant differences occurred between the caffeine drinkers and the decaff drinkers, in the birthweight of their babies or the frequency of preterm delivery: even among women who drank more than seven cups of coffee a day.

The new study does have its critics:

Dr. Carolyn Westhoff, a professor of obstetrics and gynecology, and of epidemiology, at Columbia University Medical Center, had reservations about the study, noting that miscarriage is difficult to study or explain. She said that most miscarriages resulted from chromosomal abnormalities, and that there was no evidence that caffeine could cause those problems.

“Just interviewing women, over half of whom had already had their miscarriage, does not strike me as the best way to get at the real scientific question here,” she said. “But it is an excellent way to scare women.”

What's the take home message?

“Moderation in all things is still an excellent rule,” Dr. Westhoff said. “I think we tend to go overboard on saying expose your body to zero anything when pregnant. The human race wouldn’t have succeeded if the early pregnancy was so vulnerable to a little bit of anything. We’re more robust than that.”