Consuming the amount of caffeine equivalent to that found in one to two cups of coffee does not appear to increase a pregnant woman's chances of having a miscarriage. However, consuming the amount of caffeine contained in five or more cups of coffee a day appears to double miscarriage risk, according to results of a study by researchers at the National Institute of Child Health and Human Development and the University of Utah in Salt Lake City. The study appears in the November 25 issue of the New England Journal of Medicine.
Caffeine and related compounds are found not only in coffee, but also in tea, soft drinks, and chocolate. About 200 milligrams of caffeine are found in one-and-a-half to two cups of brewed coffee or two cups of brewed tea, according to NIH's National Institute of Environmental Health Sciences. (A review of the research on caffeine, fertility, pregnancy, and breast-feeding is available on the NIEHS website: http://cerhr.niehs.nih.gov/genpub/topics/caffeine.html.)
Using a new method to estimate overall caffeine consumption, the researchers analyzed stored blood samples from a large group of women. Specifically, they measured blood levels of paraxanthine, a substance produced when caffeine is broken down by the liver. Caffeine reaches high levels in the blood shortly after consumption, but then plummets a short time later. Because paraxanthine remains in the blood longer--and at more consistent levels--than does caffeine, the investigators believe it is a more accurate barometer of daily caffeine consumption.
"Because many studies of caffeine consumption have relied on self reporting, it has been difficult to gauge the effects of
caffeine," said Duane Alexander, M.D., Director of the NICHD. "This research not only shows a risk of miscarriage from
consuming large amounts of caffeine, it also provides a valuable research tool for other investigators st
Contact: Bob Bock
NIH/National Institute of Child Health and Human Development