Seven randomised controlled trials (RCTs) (n=5,969 with 2,982 who received intervention and 2,987 placebo) were included in the review. Four RCTs were of high quality (two scored 4 and two scored 3 on the Jadad scale) and three RCTs were of low quality (one scored 2 and two scored 1 on the Jadad scale).
There was a statistically significant increase in gestational hypertension in women who received vitamin C and E compared to placebo (RR 1.3, 95% CI 1.08 to 1.57; three RCTs) with no evidence of statistical heterogeneity (p=0.27).
There were no statistically significant differences between the two groups in incidence of pre-eclampsia (seven RCTs), incidence of preterm delivery (five RCTs), small for gestational age in neonates (five RCTs) and low birth weight neonates (three RCTs). There was evidence of statistical heterogeneity for studies that assessed pre-eclampsia (p=0.019).
Sensitivity analyses for studies that reported data on pre-eclampsia did not significantly alter the results.
There was evidence of publication bias for studies that reported incidence of pre-eclampsia and small for gestational age.