Dysfunction in the antioxidant defenses has been suggested as an important factor in the pathogenesis of preeclampsia. Laboratory markers in women with preeclampsia support this, although smaller randomized trials of antioxidant supplements have yielded conflicting results. The Australian Collaborative Trial of Supplements (ACTS) was a randomized, placebo-controlled trial that examined whether supplementation with vitamins C and E reduced serious maternal and infant complications in 1,877 nulliparous women.

Patients were randomized to receive vitamin C (1,000 mg) and vitamin E (400 IU) or placebo daily, beginning between 14 and 22 weeks’ gestation. Participants were required to have singleton pregnancies and normal blood pressure at trial entry. Most of the participants (95 percent) were white, and the average age was 26 years. Primary outcome measures included maternal preeclampsia, infant death or serious infant outcome (e.g., severe respiratory distress syndrome, necrotizing enterocolitis), and small infant for gestational age.

There were no differences in the risks of preeclampsia or other primary outcome measures between the supplementation and placebo groups. Furthermore, among women who developed preeclampsia, there were no differences between the two groups in the time of onset or the severity.

One limitation noted by the authors was that the trial participants had a high dietary intake of vitamins C and E at baseline, so the results may not be applicable to women with low dietary antioxidant intake. Trials with women at increased risk of preeclampsia are ongoing. However, based on their findings, the authors do not recommend vitamin C or E supplementation to reduce preeclampsia or other serious outcomes.