High doses of daily caffeine during pregnancy—whether from coffee, tea, caffeinated soda or hot chocolate—cause an increased risk of miscarriage, according a new study by the Kaiser Permanente Division of Research. The study controlled, for the first time, pregnancy-related symptoms of nausea, vomiting, and caffeine aversion that tended to interfere with the determination of caffeine’s true effect on miscarriage risk. The research appears in the current online issue of American Journal of Obstetrics and Gynecology.
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, PhD, 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. Women who consumed less than 200 mg of caffeine daily had more than 40% increased risk of miscarriage.
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.