The Journal: The Lancet, online

The Study: Pregnant women who are at increased risk of a condition marked by elevated blood pressure don't benefit from high doses of vitamin C and E supplements. A previous study had suggested the vitamins might be beneficial. And to the surprise of the researchers from King's College London, their study also produced evidence that the high levels of these antioxidants might even increase the risk of low birthweight in the newborns.

The researchers selected 2,404 pregnant women from 25 U.K. hospitals based on their high risk of pre-eclampsia, a condition in which women develop high blood pressure during pregnancy. From the first day of the second trimester through delivery, about half the women took daily doses of 1,000 mg of vitamin C and 400 IU (international units) of vitamin E and the other half took a sugar pill. The incidence of pre-eclampsia was similar for both groups: 15% of the women taking the active supplements developed the condition, compared to 16% of the placebo group.

Birthweight was another matter. More babies (28%) were born underweight to women taking the high-dose supplements of vitamins C and E than to those on placebo (24%). Women on the antioxidants also required more treatment, including medication to control their high blood pressure.

What It Means: The results are surprising for two reasons. A small trial in 1999 suggested that these two antioxidants—in the same dosage as in this study—might reduce the risk of pre-eclampsia. In addition, the daily doses in this study fell beneath the maximum daily recommended intake for pregnant women.

Small amounts of vitamins C and E—such as found in multivitamin supplements specifically formulated for pregnant women—apparently pose no problems, however. As always, a proper diet during pregnancy, which includes vitamins and nutrients like folic acid, is absolutely critical for fetal development.

From the Archives:
12/05/05 The Year in Medicine
11/22/04 To E or not to E