A randomised, double-blind placebo-controlled trial of ascorbic acid supplementation for the prevention of preterm labour. Vitamin C and vitamin E in pregnant women at risk for pre-eclampsia (VIP trial): randomised placebo-controlled trial. Vitamins C and E and the risks of preeclampsia and perinatal complications.
In a previous study from this institution, patients at high risk for preterm labour were screened for the presence of bacterial vaginosis (BV). When BV was present, they were randomised to receive either treatment (metronidazole) or placebo (vitamin C). There were significantly more patients with preterm labour in the metronidazole group. The aim of this double-blind randomised placebo-controlled trial study was to determine whether vitamin C could indeed reduce the recurrence risk of preterm labour. Patients with a history of preterm labour in a preceding pregnancy were randomised to receive 250 mg vitamin C or a matching placebo twice daily until 34 weeks' gestation. They attended a dedicated premature labour clinic. Significantly more women delivered before term in the group that received vitamin C, but there was no difference in the outcome of the babies between the two groups. Supplementation with vitamin C did not prevent premature labour. 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 alpha 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 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. Supplementation with antioxidant vitamins has been proposed to reduce the risk of preeclampsia and perinatal complications, but the effects of this intervention are uncertain.
                We conducted a multicenter, randomized trial of nulliparous women between 14 and 22 weeks of gestation. Women were assigned to daily supplementation with 1000 mg of vitamin C and 400 IU of vitamin E or placebo (microcrystalline cellulose) until delivery. Primary outcomes were the risks of maternal preeclampsia, death or serious outcomes in the infants (on the basis of definitions used by the Australian and New Zealand Neonatal Network), and delivering an infant whose birth weight was below the 10th percentile for gestational age.
                Of the 1877 women enrolled in the study, 935 were randomly assigned to the vitamin group and 942 to the placebo group. Baseline characteristics of the two groups were similar. There were no significant differences between the vitamin and placebo groups in the risk of preeclampsia (6.0 percent and 5.0 percent, respectively; relative risk, 1.20; 95 percent confidence interval, 0.82 to 1.75), death or serious outcomes in the infant (9.5 percent and 12.1 percent; relative risk, 0.79; 95 percent confidence interval, 0.61 to 1.02), or having an infant with a birth weight below the 10th percentile for gestational age (8.7 percent and 9.9 percent; relative risk, 0.87; 95 percent confidence interval, 0.66 to 1.16).
                Supplementation with vitamins C and E during pregnancy does not reduce the risk of preeclampsia in nulliparous women, the risk of intrauterine growth restriction, or the risk of death or other serious outcomes in their infants. (Controlledtrials.com number, ISRCTN00416244.).
                Copyright 2006 Massachusetts Medical Society.
The data are too few to say if vitamin C supplementation either alone or in combination with other supplements is beneficial during pregnancy. Preterm birth may have been increased with vitamin C supplementation.
[Note: The 32 citations in the awaiting classification section of the review may alter the conclusions of the review once assessed.]