Caffeine drinkers more likely to miscarry

Jan 21, 2008, Julie Steenhuysen, REUTERS NEWS AGENCY for the Toronto Star

2 or more coffees a day doubles risk, study says

CHICAGO–Pregnant women who drink two or more cups of coffee a day have twice the risk of having a miscarriage as those who avoid caffeine, say U.S. researchers.

The study says there is strong evidence that high caffeine doses during pregnancy – 200 milligrams or more per day or the equivalent of two cups of coffee – significantly increase the risk of miscarriage.

The study's author says the research may finally put to rest conflicting reports about the caffeine-miscarriage link.

"Women who are pregnant or are actively seeking to become pregnant should stop drinking coffee for three months or hopefully throughout pregnancy," said Dr. De-Kun Li of Kaiser Permanente Division of Research. His study appears today in the American Journal of Obstetrics and Gynecology.

"There has been a lot of uncertainty about this," Li said in a telephone interview. "There was no firm advice from professional societies to say what a pregnant woman should do about caffeine intake."

Li said up to 18 studies have linked the stimulant and miscarriages, but the association was clouded by the fact that many pregnant women avoid caffeine because it makes them feel nauseous, which could skew results.

Li and his colleagues used data from 1,063 pregnant members of the Kaiser Permanente health plan in San Francisco from October 1996 through October 1998. None of the women changed their caffeine consumption during pregnancy.

They found women who consumed the equivalent of two or more cups of coffee, or five 12-ounce cans of caffeinated pop, were twice as likely to miscarry as pregnant women who avoided caffeine.

Researchers believe the culprit is caffeine, not other coffee chemicals, because they saw increased risk from pop, tea and other caffeinated beverages.

Li said many researchers think caffeine stresses the fetus's immature metabolism. It may also decrease blood flow in the placenta, which could harm the fetus.

"To me, the safe dose is zero," Li said. "If you really have to drink coffee, try to limit it to one cup or at the most two cups." Or better yet, switch to decaffeinated beverages, he added.

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