Vitamin C supplementation in pregnancy

BackgroundVitamin E supplementation may help reduce the risk of pregnancy complications involving oxidative stress, such as pre-eclampsia. There is a need to evaluate the efficacy and safety of vitamin E supplementation in pregnancy.ObjectivesTo assess the effects of vitamin E supplementation, alone or in combination with other separate supplements, on pregnancy outcomes, adverse events, side-effects and use of health services.Search strategyWe searched the Cochrane Pregnancy and Childbirth Group Trials Register (23 June 2004), the Cochrane Central Register of Controlled Trials (The Cochrane Library, Issue 2, 2004), MEDLINE (1966 to May 2004), Current Contents (1998 to May 2004) and EMBASE (1980 to May 2004).Selection criteriaAll randomised or quasi-randomised controlled trials evaluating vitamin E supplementation in pregnant women. We excluded interventions using a multivitamin supplement that contained vitamin E.Data collection and analysisTwo authors independently assessed trials for inclusion, extracted data and assessed trial quality.Main resultsFour trials, involving 566 women either at high risk of pre-eclampsia or with established pre-eclampsia, were eligible for this review. All trials assessed vitamin E in combination with other supplements and two trials were published in abstract form only. No difference was found between women supplemented with vitamin E in combination with other supplements during pregnancy compared with placebo for the risk of stillbirth (relative risk (RR) was 0.77, 95% confidence intervals (CI) 0.35 to 1.71, two trials, 339 women), neonatal death (RR 5.00, 95% CI 0.64 to 39.06, one trial, 40 women), perinatal death (RR 1.29, 95% CI 0.67 to 2.48, one trial, 56 women), preterm birth (RR 1.29, 95% CI 0.78 to 2.15, two trials, 383 women), intrauterine growth restriction (RR 0.72, 95% CI 0.49 to 1.04, two trials, 383 women) or birthweight (weighted mean difference -139.00 g, 95% CI -517.68 to 239.68, one trial, 100 women), using fixed-effect models. Substantial heterogeneity was found for pre-eclampsia. Women supplemented with vitamin E in combination with other supplements compared with placebo were at decreased risk of developing clinical pre-eclampsia (RR 0.44, 95% CI 0.27 to 0.71, three trials, 510 women) using fixed-effect models; however, this difference could not be demonstrated when using random-effects models (RR 0.44, 95% CI 0.16 to 1.22, three trials, 510 women). There were no differences between women supplemented with vitamin E compared with placebo for any of the secondary outcomes.Authors' conclusionsThe data are too few to say if vitamin E supplementation either alone or in combination with other supplements is beneficial during pregnancy.Rumbold A, Crowther C