Caffeine during pregnancy increases miscarriage risk, study suggests


A new study by the Kaiser Permanente Division of Research suggests that a high intake of caffeine during pregnancy may lead to an increased risk of miscarriage, regardless of its source.

While previous research showed a link between caffeine consumption and miscarriage, this is the first study to thoroughly control for morning sickness, which typically causes many women to avoid caffeine, explained De-Kun Li, MD, Ph.D., an investigator with the Kaiser Permanente Division of Research and lead investigator of the study. “This study strengthens the association between caffeine and miscarriage risk because it removes speculation that the association was due to reduced caffeine intake by healthy pregnant women,” Li said.

To address that speculation, the study, which looked at 1,063 pregnant Kaiser Permanente members in San Francisco from October 1996 through October 1998, examined the caffeine effect among women who never changed their pattern of caffeine consumption during their pregnancy. Kaiser Permanente is the nation’s largest health plan with 8.7 million members, 416 medical offices and 32 hospitals in nine states and the District of Columbia.

Women who consumed 200 mg or more of caffeine per day (two or more cups of regular coffee or five 12-ounce cans of caffeinated soda) had twice the miscarriage risk as women who consumed no caffeine, said Li.

The increased risk of miscarriage appeared to be due to the caffeine itself, rather than other possible chemicals in coffee because caffeine intake from non-coffee sources such as caffeinated soda, tea and hot chocolate showed a similar increased risk of miscarriage.

“The main message for pregnant women from these findings is that they probably should consider stopping caffeine consumption during pregnancy because this research provides clearer and stronger evidence that high doses of caffeine intake during pregnancy can increase the risk of miscarriage,” said Li.

The reasons that caffeine can harm a fetus have been suspected for some time. Caffeine crosses through the placenta to the fetus, but can be difficult for the fetus to metabolize because of the under-developed metabolic system. Caffeine also may influence cell development and decrease placental blood flow, which may lead to an adverse effect on fetal development.

So what’s a fatigued mom-to-be supposed to do for her daily energy jolt?

“If you definitely need caffeine to get you going, try keeping it to one cup or less a day. Avoiding it may be even better. Consider switching to decaffeinated coffee and other decaffeinated beverages during your pregnancy,” said Tracy Flanagan, MD, Director of Women’s Health, Kaiser Permanente Northern California. “Learn to perk up instead with natural energy boosts like a brisk walk, yoga stretches, snacking on dried fruits and nuts.”