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Health & Pregnancy

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Moderate Caffeine Consumption During Pregnancy Does Not Increase Miscarriage Risk

WebMD Health News

Nov. 24, 1999 (New York) -- Pregnant women who can't seem to give up their morning cup of coffee or tea may be interested in the results of a new study showing that moderate caffeine consumption does not increase the risk of miscarriage. Although some studies have indicated that caffeine could increase the risk of miscarriage, this study, appearing in the Nov. 25 issue of TheNew England Journal of Medicine, found that rates were only affected in women who consumed caffeine in amounts equivalent to more than five cups of coffee per day.

The study consisted of blood samples obtained from pregnant women enrolled in the Collaborative Perinatal Project, which was conducted from 1959 to 1966. Serum paraxanthine, the primary by-product of caffeine, was measured in almost 600 women who had miscarriages at less than 140 days into their pregnancy. They compared them to nearly 2,600 women who gave birth to live infants at 28 weeks' gestation or later and had blood drawn on the same day of gestation as the women who miscarried. They found the mean serum paraxanthine concentration was higher in the women who had miscarriages than in the other women.

"The reason we decided to use this particular database was because per-capita coffee consumption in the U.S. peaked around 1962, so it was convenient that we were able to access a database of pregnant women who were pregnant predominantly in the early 1960s," the study's lead author, Mark A. Klebanoff, MD, MPH, tells WebMD. "More recent studies have actually had a hard time recruiting large numbers of women who consumed large amounts of caffeine while pregnant." Klebanoff is a medical officer at the National Institute of Child Health and Human Development, in Bethesda, Md.

Women with paraxanthine levels higher than 1,845 nanograms per milliliter of blood had the greatest increased risk of miscarriage. Those with concentrations above 1,845 nanograms per milliliter had nearly double the risk.

Klebanoff says a conservative estimate would be that more than five cups of coffee per day would be needed to achieve a blood level of 1,845 nanograms per milliliter or higher. A typical cup of brewed coffee has about 100 milligrams of caffeine and a cup of tea has about 40 milligrams.

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