Moderate Caffeine Consumption During Pregnancy Does Not Increase Miscarriage Risk
WebMD News Archive
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.