Large Vitamin Doses Do Not Prevent, May Increase Risk of Preeclampsia


Based on the premise that oxidative stress is a factor in the development of preeclampsia, a dangerous increase in blood pressure during pregnancy, researchers from the University of Pittsburgh have found that, despite an earlier, smaller study that produced positive effects, large amounts of vitamins C and E do not prevent the condition.

Dr. James Roberts, lead author of the report published in the New England Journal of Medicine, studied nearly 10,000 women between July 2003 and February 2009 who were taking 1,000 milligrams of vitamin C or 400 IU of vitamin E daily and actually came to the conclusion that the vitamins may actually worsen the risk of high blood pressure during pregnancy by 10%.

The trial included only women who were pregnant for the first time and at low risk for preeclampsia. They began taking the vitamins between the ninth and 16th week of pregnancy and continued up to delivery.


Preeclampsia, present in about 15% of premature births, involves high blood pressure and excess protein in the urine and usually presents after the 20th week of pregnancy. If left untreated it can lead to severe and sometimes fatal complications for both mother and baby. Preeclampsia is a major cause of death among pregnant women in developing countries. In most pregnancies, there are no preventative therapies known.

Previously, a study of 283 women found that vitamins C and E reduced the risk of preeclampsia by 60%, however the result was controversial as only 17% of women were taking prenatal vitamins and further studies have failed to produce the same effect. The original study suggested that the vitamins were antioxidants, preventing damage from free radicals that may prevent the placenta from developing normally and could interfere with blood flow from mother to baby.

Dr. Roberts stresses to women to continue to take prenatal vitamins as the doses of C and E are much lower than those used in the study and in line with the current recommendations for nutrients during pregnancy. "This has absolutely no relevance to the use of standard doses of vitamin C and E as part of prenatal vitamins," he said. "These (study) doses were enormously higher, where they act as a drug rather than a vitamin."

"In the United States, obstetricians generally recommend that pregnant women take a multivitamin formulated for pregnancy, especially if they aren't eating a well-balanced diet," added Dr. Catherine Spong of the National Institute of Child Health and Human Development, which helped pay for the study.

Source reference:
Roberts JM, et al "Vitamins C and E to prevent complications of pregnancy-associated hypertension" N Engl J Med 2010; 362: 1282-91. ( number, NCT00135707 [] ).