The risk of miscarriage may significantly increase for pregnant women who drink two cups of coffee or more per day, according to a new research available Monday.

Researchers at the medical research institute Kaiser Permanente in Oakland studied 1,063 women in the San Francisco area early in their pregnancies.

They questioned the women in detail about their beverage consumption and whether they were experiencing morning sickness.

Those women who consumed 200 milligrams of caffeine or more a day were about twice as likely to miscarry, the researchers reported on the website of the American Journal of Obstetrics and Gynecology.

That's about the amount of caffeine in two eight-ounce cups of coffee, five 12-ounce cans of soda or six cups of tea, according to the study.

The findings are consistent with those of earlier studies, which have found an increased risk of miscarriage from daily consumption of about 150 to 300 milligrams of caffeine, said De-Kun Li, a reproductive and perinatal epidemiologist at Kaiser Permanente, who led the study..

"But we went one step further in determining whether it was the caffeine itself or it was women changing their drinking pattern," he said. "My hope is our study will remove that uncertainty. I think this should put the argument to rest."

The study provides the most convincing evidence to date of such a link, the researchers said.

Research previously indicated an increased risk, but scientists were unsure whether those findings were affected by the fact that women having morning sickness might be less likely to drink coffee or other caffeinated beverages.

Based on the findings, Li recommended that women who are pregnant or trying to get pregnant minimize caffeine intake. "If they have to drink caffeine-containing beverages, they should reduce the amount to one cup a day at the most," he said.

(Xinhua News Agency January 22, 2008)