Prevention of pre-eclampsia with low-dose aspirin or vitamins C and E in women at high or low risk: a systematic review with meta-analysis.

The aim of this study is to review literature about the efficacy of low dose aspirin (LDA) and vitamins C/E (VCE) to prevent pre-eclampsia in women at high and low risk. Randomized clinical trials were included and stratified for high and low risk women. Inclusion criteria were: assignment of patients in treated or placebo groups, definition of pre-eclampsia according to the guidelines of the International Society for the Study of Hypertension in Pregnancy. Exclusion criteria were: omitting at least one of the inclusion criteria, trials involving women with pre-eclampsia at trial entry, studies investigating hypertensive disorders other than pre-eclampsia, prophylaxis of intrauterine growth restriction with low-dose aspirin or vitamins C/E, non-randomized studies and data reported in graphs or percentages. The incidence of pre-eclampsia, perinatal outcomes and adverse effects attributable to LDA and VCE were compared between treated women and placebo. Inter-studies heterogeneity was tested. P<0.05 was considered significant. pooled odds ratios (OR) with 95% confidence intervals (95% CI) were calculated. PRISMA guidelines were followed. Fifteen studies were pooled. LDA did not decrease the incidence of pre-eclampsia in high-risk (396/5025 - 8% vs placebo: 464/5027 - 9%; P=0.05; OR: 0.72; 95% CI: 0.51-1.00) and low-risk (137/4939 - 3% vs placebo: 166/4962 - 3%; P=0.10; OR: 0.82; 95% CI: 0.65-1.04) women. Similarly, VCE did not reduce the incidence of pre-eclampsia in high-risk (VCE: 250/1744 - 14% vs placebo: 275/1741 - 16%; P=0.24; OR: 0.84; 95% CI: 0.63-1.12) and low-risk (VCE: 56/935 - 6% vs placebo 47/942 - 5%; P=0.57; OR: 1.20; 95% CI: 0.82-1.75) women. In high-risk women, other hypertensive disorders were more frequent in VCE (121/1692 - 7%) than placebo (79/1693 - 5%; P=0.002). Perinatal outcomes were not improved by LDA or VCE. there is no evidence to support the administration of LDA or VCE to prevent pre-eclampsia.