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NIH Research Matters

April 19, 2010

Vitamins Fail to Help Blood Pressure Disorders of Pregnancy

Taking vitamin C and E supplements starting in early pregnancy does not reduce the risk for pregnancy-associated hypertension and its complications, according to a new study.

Photo of a pregnant woman holding vitamins in front of her belly.

High blood pressure can be dangerous for both the mother and the fetus. It can harm the mother's kidneys and other organs, and can cause low birth weight and early delivery. In the most serious cases, the mother can develop a condition called preeclampsia that can threaten the lives of both mother and fetus.

Some small studies suggested that vitamins C and E could reduce the risk of preeclampsia. Vitamins C and E are antioxidants—molecules that neutralize harmful byproducts of the body's use of oxygen called free radicals. Researchers theorized that free radicals might prevent the placenta from developing properly and interfere with blood flow from the mother to the baby.

A team of researchers led by Dr. James M. Roberts of the University of Pittsburgh set out to more thoroughly investigate the effects of vitamins C and E in pregnancy. Their large-scale study, at 16 sites across the nation, was funded by NIH’s Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD), National Heart, Lung and Blood Institute (NHLBI) and National Center for Research Resources (NCRR).

The researchers enrolled over 10,000 generally healthy women in their 9th to 16th weeks of pregnancy and followed them to delivery. They included only women who were giving birth for the first time—a group at higher risk for developing hypertensive disorders of pregnancy. The women received either daily supplements of vitamins C and E, with about 10 times the amount in typical prenatal vitamins, or a placebo. The women took these in addition to any pregnancy vitamins they were already taking.

In the April 8, 2010, issue of the New England Journal of Medicine, the researchers reported that the supplements failed to reduce the risk of pregnancy-associated hypertension and its complications. They looked at pregnancy-associated hypertension, seizure, protein in the urine (a sign of stress on the kidneys), preeclampsia, blood or liver abnormalities, loss of the pregnancy, an underweight baby and preterm delivery. The rates didn’t differ statistically between the 2 groups for any of these outcomes.

"The study results effectively rule out vitamin C and E supplements as a means to prevent the hypertensive disorders seen in pregnancy," says Dr. Alan E. Guttmacher, acting director of NICHD.

Although these results don’t address whether free radical damage can lead to preeclampsia, study co-author Dr. Catherine Y. Spong of NICHD says they do show that treatment with vitamins C and E won’t prevent the condition.

"These results are very useful," Spong says. "In this case, it shows us that what originally appeared to be a promising treatment did not actually offer any benefit clinically."

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Editor: Harrison Wein, Ph.D.
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NIH Research Matters is a weekly update of NIH research highlights from the Office of Communications and Public Liaison, Office of the Director, National Institutes of Health.

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This page last reviewed on December 3, 2012

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