WESTPORT, Sep 03 (Reuters Health) - Prenatal supplementation with vitamins C and E can help prevent the onset of pre-eclampsia in women at high risk for this complication during pregnancy, according to British investigators.

It remains to be determined whether or not this intervention will also be effective in low-risk women, or in larger clinical studies, Dr. Lucy C. Chappell, of St. Thomas' Hospital, and researchers there and elsewhere in London point out.

The team identified 283 pregnant women at high risk of developing pre-eclampsia, based on a history of the disorder or abnormal results on a two-stage uterine artery Doppler analysis. The women were randomized to take vitamin C (1,000 mg/day) and vitamin E (400 IU/day), or placebo, beginning at 16 to 22 weeks of gestation and continuing until delivery.

During the study, 17% of women assigned to placebo developed pre-eclampsia compared with only 8% of those in the supplementation group, giving a significant odds ratio of 0.39, Dr. Chappell and others report in the September 4th issue of The Lancet. When only those women who completed the study were included in the analysis, the risk was reduced still more, with an odds ratio of 0.24.

In addition, supplementation with vitamins C and E lowered the ratio of plasminogen-activator inhibitor 1 to plasminogen-activator inhibitor.

This finding supports the hypothesis that oxidative stress plays a role in the etiology of pre-eclampsia and that antioxidant therapy has a role in its prevention, the authors say.

But elsewhere in the journal, Drs. James M. Roberts and Carl A. Hubel caution against overinterpreting and overgeneralizing the new data.

The editorialists, both researchers at the University of Pittsburgh in Pennsylvania, expect that vitamin C and E supplementation "will undoubtedly" be widely adopted before its safety and efficacy are confirmed in larger studies. They remind readers of a similar scenario that occurred when calcium and aspirin were reported to prevent pre-eclampsia, based on results from small studies--results that were not confirmed in larger trials.

Nevertheless, Drs. Roberts and Hubel believe that the antioxidant vitamins represent "...a relevant target for future clinical trials." Such trials should include a demonstration of safety, "...especially for the infant," they advise.