Oxidative stress could play a part in pre-eclampsia, and there is some evidence to suggest that vitamin C and vitamin E supplements could reduce the risk of the disorder. Our aim was to investigate the potential benefit of these antioxidants in a cohort of women with a range of clinical risk factors.

We did a randomised, placebo-controlled trial to which we enrolled 2410 women identified as at increased risk of pre-eclampsia from 25 hospitals. We assigned the women 1000 mg vitamin C and 400 IU vitamin E (RRR α tocopherol; n=1199) or matched placebo (n=1205) daily from the second trimester of pregnancy until delivery. Our primary endpoint was pre-eclampsia, and our main secondary endpoints were low birthweight (<2�5 kg) and small size for gestational age (<5th customised birthweight centile). Analyses were by intention to treat. This study is registered as an International Standard Randomised Controlled Trial, number ISRCTN 62368611.

Of 2404 patients treated, we analysed 2395 (99�6%). The incidence of pre-eclampsia was similar in treatment and placebo groups (15% [n=181] vs 16% [n=187], RR 0�97 [95% CI 0�80–1�17]). More low birthweight babies were born to women who took antioxidants than to controls (28% [n=387] vs 24% [n=335], 1�15 [1�02–1�30]), but small size for gestational age did not differ between groups (21% [n=294] vs 19% [n=259], 1�12 [0�96–1�31]).

Concomitant supplementation with vitamin C and vitamin E does not prevent pre-eclampsia in women at risk, but does increase the rate of babies born with a low birthweight. As such, use of these high-dose antioxidants is not justified in pregnancy.