Women who rapidly metabolize caffeine may be at risk for having a miscarriage, unlike women who take longer to clear caffeine from their bodies.
There is a longstanding debate about whether caffeine intake during pregnancy can influence a woman's risk for miscarriage. Some studies have shown a possible risk associated with caffeine, but others have not.
Researchers from the International Epidemiology Institute in Rockville, Maryland, and Vanderbilt University in Nashville, Tennessee hypothesized that if two women drank the same amount of coffee, the woman whose body broke down caffeine at a slower rate--and thus would have the stimulant in her system longer--would have a greater risk of miscarriage than a woman whose body cleared caffeine more rapidly.
The study included 101 women who had a miscarriage during the first trimester for unknown reasons and a "control" group of 953 pregnant women in the first trimester of pregnancy. The investigators found that caffeine intake was a risk factor for miscarriage only for those women who broke down caffeine faster, not slower, than other women.
The researchers stressed, however, that the findings need to be confirmed in future studies with larger numbers of women. "These results could have come about through many reasons other than a cause-effect relationship," she said.
In the study, the risk was highest for those fast metabolizers who consumed 300 mg or more of caffeine per day.
On average, there are 35 mg of caffeine in a 12-ounce cola, 115 mg in 5 ounces of regular-brew coffee and 40 mg in 5 ounces of regular American tea.
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