Caffeine-Miscarriages Link Studied

Wednesday, December 20th 2000, 12:00 am

By: News On 6

Five cups of coffee per day more than doubles a pregnant woman's risk of a miscarriage, according to perhaps the most rigorous study yet to focus on the possible link between caffeine and miscarriage.

Some doctors have long suspected a connection and urge pregnant women to avoid caffeine. However, even this study likely won't end the doubts.

Unlike most past research, the latest study looked at women in early pregnancy, when most miscarriages happen. It also tried to account for a separate risk from genetic defects in fetuses and a possible risk from smoking.

The research team in Sweden and the United States, which was to publish its findings in Thursday's issue of the New England Journal of Medicine, found that the equivalent of one-to-three cups of American coffee increases the risk of miscarriage by 30 percent. Three-to-five cups raises the risk by 40 percent.

Five cups or more yields more than double the risk.

The study involved 562 women who had miscarriages at between six to 12 weeks of pregnancy. Since they were Swedish, they often drank stronger coffee than Americans. A cup of Swedish coffee typically carries about 180 milligrams of caffeine, compared to the 100 milligrams in a typical American cup of coffee.

Tea, cocoa and sodas in equal volumes normally contain less caffeine than coffee. But the study suggests a similar effect on miscarriage for these drinks and in caffeine-carrying medications, if enough is consumed.

The study was directed by Dr. Sven Cnattingius of the Karolinska Institute in Stockholm. In an interview, he suggested pregnant women curtail their coffee to the equivalent of about two American cups per day.

The Food and Drug Administration and the March of Dimes, which funds research on birth defects, have both advised pregnant women to curtail caffeine.

The researchers also tried to account for the effects of morning sickness, which has tended to exaggerate the impact of caffeine in earlier studies because nausea is more common in pregnant women with healthy fetuses. Since morning sickness gives many such women a distaste for coffee, more unhealthy fetuses are found among coffee drinkers.

Dr. Mark Klebanoff, at the National Institute of Child Health and Human Development, who was familiar with the findings, said it is still possible that morning sickness skews the results.

``I think it will never be completely possible to rule it out, no matter how good a study you do,'' he said.

But he said this study is probably the strongest yet, because it was specifically designed to answer whether caffeine promotes miscarriage. Other studies used data initially collected to resolve other questions.

Robert Nelson, president of the New York-based National Coffee Association trade group, argued that research indicates pregnant women can drink perhaps up to four cups of coffee a day without apparent risk.

He believes, like Klebanoff, that studies tie coffee to miscarriage because women with healthy pregnancies tend to develop an aversion for coffee and other drinks with strong aromas.

``The body of evidence after decades, including this study, confirms the fact that coffee can be consumed safely in moderate quantities in pregnant women,'' he said.

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On the Net:

http://www.nejm.org

Earlier research: http://www.nichd.nih.gov/new/releases/caff99.htm

Coffee association: http://www.ncausa.org