January 23, 2008 (Canwest News Service) – California researchers have found that if pregnant women have more than 200 mg of caffeine per day, they are twice as likely to miscarry than women who avoid caffeine…

In what is believed the clearest and strongest evidence yet linking caffeine to miscarriage, California researchers who followed more than 1,000 pregnant women found those who consumed 200 mg or more of caffeine daily — the equivalent of two cups of regular coffee, or five, 12-ounce cans of caffeinated pop — had twice the risk of miscarriage as women who avoided caffeine.

Even women who consumed less that 200 mg of caffeine a day had a 42% increased risk of losing the pregnancy…

Past studies have shown a link between caffeine and miscarriage, but there has been a complicating factor: Women who get morning sickness often give up coffee. And these women are less likely to have a miscarriage in the first place, as morning sickness is one sign of a healthy pregnancy…

Dr. Li’s study is the first to “control” for morning sickness, meaning scientists took it into account before tallying up the final results. About 15% of “clinically recognized” pregnancies end in miscarriage…

Caffeine readily crosses the placental barrier, so it can go straight to the fetus. The earlier the exposure, the less likely the fetus is to metabolize it because of an under-developed metabolic system. As well, caffeine, particularly at high doses, makes blood vessels contract.

If that contraction is severe enough, it may reduce blood flow to the placenta. “That can have detrimental effects to the fetus as well,” Dr. Li said.

His team recruited 1,063 San Francisco women from October of 1996 to October of 1998. Women were recruited early in their pregnancy — as early as four weeks gestation — “so we were able to capture a lot of miscarriages that most studies missed,” Dr. Li said…

Overall, 172 women, or 16%, miscarried. The higher the intake of caffeine from any source — coffee, tea, caffeine-containing soft drinks or hot chocolate — the greater the risk of early or late miscarriage. Compared with non-users, women who consumed 0-200 mg of caffeine daily had an increased risk of miscarriage (15% versus 12%). The risk was higher (25%) in women who consumed more than 200 mg of caffeine daily.

More… (source)

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