A Cochrane review 3 (abstract , review [Abstract]) included 10 studies with a total of 6 533 subjects. For the majority of trials, the antioxidant assessed was combined vitamin C and E therapy. There was no significant difference between antioxidant and control groups for the relative risk of pre-eclampsia (RR 0.73, 95% CI 0.51 to 1.06; 9 trials, 5446 women) or any other primary outcome: severe pre-eclampsia (RR 1.25, 95% CI 0.89 to 1.76; 2 trials, 2495 women), preterm birth (before 37 weeks) (RR 1.10, 95% CI 0.99 to 1.22; 5 trials, 5198 women), small-for-gestational-age infants (RR 0.83, 95% CI 0.62 to 1.11; 5 trials, 5271 babies) or any baby death (RR 1.12, 95% CI 0.81 to 1.53; 4 trials, 5144 babies). Women allocated antioxidants were more likely to self-report abdominal pain late in pregnancy (RR 1.61, 95% CI 1.11 to 2.34; 1 trial, 1745 women), require antihypertensive therapy (RR 1.77, 95% CI 1.22 to 2.57; 2 trials, 4272 women) and require an antenatal hospital admission for hypertension (RR 1.54, 95% CI 1.00 to 2.39; 1 trial, 1877 women). However, for the latter two outcomes, this was not clearly reflected in an increase in any other hypertensive complications.
Comment: The quality of evidence is downgraded by inconsistency (variability in results across studies).
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