Antioxidants seem not to prevent pregnancy-associated hypertension

Taking supplements with vitamin C and vitamin E starting in early pregnancy may not reduce the risk of hypertensive disorders such as preeclampsia during pregnancy, says a new study.

In the randomized controlled trial, over 10,000 pregnant women were randomly assigned to begin daily supplementation containing 1,000 mg of vitamin C and 400 IU of vitamin E or a matching placebo in addition to any pregnancy vitamins they may have been taking (1). Starting in the ninth to 16th weeks of pregnancy they were followed to delivery.

The results showed that the combined rates of pregnancy-associated hypertension, seizure, protein in the urine, pre-eclampsia, blood or liver abnormalities, loss of the pregnancy, an underweight baby and preterm delivery did not differ statistically between the two groups. The combined rate of complications was 6.1 percent among those taking the study vitamins and 5.7 percent among those taking the placebo. Moreover, the results showed that there was little statistical difference in preeclampsia between the two groups: 7.2 percent among women taking vitamins versus 6.7 percent among those who took the placebo.

The researchers commented that the results effectively rule out vitamin C and E supplements as a means to prevent hypertensive pregnancy disorders.

The role of antioxidants to reduce oxidative stress has been supported by smaller clinical trials linking high dose vitamin C and E intake to fewer biomarkers for pre-eclampsia, but these findings have not been confirmed by larger studies. It is not known why some expectant mothers develop preeclampsia, although oxidative stress has been proposed to play a part.

1. Roberts J. M. et al. Vitamins C and E to prevent complications of pregnancy-associated hypertension. New Engl J Med. 2010; 362:1282–1291.