A government-sponsored study of more than 10,000 women failed to find that large doses of vitamins C and E cut the risk of complications from pregnancy-induced high blood pressure, scientists report today.
Pre-eclampsia, a condition characterized by high blood pressure and protein in the urine, occurs in up to 8% of pregnancies, says Catherine Spong, a co-author of the study in The New England Journal of Medicine. A leading cause of illness and death in pregnant women and infants, pre-eclampsia can be cured only by delivering the baby.
"It's like most pregnancy conditions: We don't have great preventative therapies," says Spong, chief of the Pregnancy and Perinatology Branch at the Eunice Kennedy Shriver National Institute of Child Health and Human Development. Only baby aspirin seems to help protect against pre-eclampsia, she says, but only in high-risk women and only by a modest 10% reduction in risk.
More than a decade ago, a British study of fewer than 300 pregnant women found that taking vitamins C and E lowered the risk of pre-eclampsia. But scientists have repeatedly failed to replicate that finding.
The new trial enrolled more women and began treatment earlier than any previous study. To join, women had to be pregnant for the first time and at low risk for pre-eclampsia. They began taking their pills between the ninth and 16th week of pregnancy and continued up to delivery.
In the end, the study "found no evidence of benefit to either the mother or the baby," says lead author James Roberts, an obstetrician/gynecologist at the University of Pittsburgh. In fact, Roberts and his collaborators at 15 other medical schools found that women randomly assigned to take the vitamins were slightly more likely to develop high blood pressure than those assigned to take placebo pills, although the difference could have been the result of chance.
Caroline Crowther, a maternal fetal medicine professor at Australia's University of Adelaide, co-wrote a similar study of nearly 2,000 women published in 2006.
"With another large trial of vitamin C and E supplementation during pregnancy now showing no benefit in reducing the risk of pre-eclampsia, they clearly cannot be recommended," Crowther said in an e-mail.
Roberts and Spong emphasized that their findings don't mean that women should stop taking prenatal vitamins.
"This has absolutely no relevance to the use of standard doses of vitamin C and E as part of prenatal vitamins," Roberts says. "These (study) doses were enormously higher, where they act as a drug rather than a vitamin."
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