The antioxidant vitamins C and E might not reduce a woman's risk of experiencing pre-eclampsia, according to a Cochrane Systematic Review.
Australian researchers reviewed ten clinical trials involving 6533 women and concluded that no significant benefits were afforded by antioxidant supplementation for reducing the risk of pre-eclampsia.
The review follows similar null results published in 2006 that, in their entirety, may close the door on research into the use of the antioxidants to reduce the risk of pre-eclampsia.
Pre-eclampsia, affecting two to three per cent of all pregnancies, occurs when a mother's blood pressure rises to the hypertensive range, and excretion of protein in the urine becomes too high. It is estimated to be responsible for about 60000 deaths worldwide.
It is not known why some expectant mothers develop pre-eclampsia, although oxidative stress has been proposed to play a part. The role of antioxidants to reduce oxidative stress had been supported by a small clinical trial that linked vitamin C and E intake to fewer biomarkers for pre-eclampsia for predominantly low-risk participants.
However, after reviewing the ten trials, five of which were deemed to be high quality, lead author Alice Rumbold from the Menzies School of Health Research in Darwin, Australia, concluded that the overall science is unconvincing.
"Evidence does not currently support routine use of antioxidant supplements during pregnancy as a means of reducing the risk of pre-eclampsia or other serious problems," she said.
Rumbold and co-workers report that no significant differences were observed between the antioxidant and control groups with respect to the risk of pre-eclampsia, severe pre-eclampsia, premature births (earlier than 37 weeks), small-for-gestational-age infants, or any baby death.
On the other hand, they did note that self-report abdominal pain late in pregnancy was more likely in the women receiving the antioxidants, with additional concerns over increases in blood pressure (hypertension)
"Evidence from this review does not support routine antioxidant supplementation during pregnancy to reduce the risk of pre-eclampsia and other serious complications in pregnancy," they concluded.
It should be stressed that expectant mothers, as well as all women of child-bearing age, should continue to eat folic acid-rich or fortified foods and/or take folic acid supplements to reduce the risk of neural tube defects.
Source: The Cochrane Database of Systematic Reviews
2007, Issue 4, doi: 10.1002/14651858.CD004227.pub3
"Antioxidants for preventing pre-eclampsia"
Authors: A. Rumbold, L. Duley, C.A. Crowther, R.R. Haslam