In fact, results from the 4-1/2-year test of nearly 5,000 women found those taking very high doses of the two vitamins were 10 percent more likely to develop high blood pressure during pregnancy than volunteers taking placebo pills.
There's no way anyone could justify treating patients with these drugs during pregnancy, Dr. James Roberts of the University of Pittsburgh, who led the study, said in a telephone interview. Clearly vitamins C and E are not an answer to the problem.
Preeclampsia is a condition that can occur during pregnancy that involves high blood pressure and excess protein in the urine. While the blood pressure increases may not be huge, preeclampsia if left untreated can lead to severe and sometimes fatal complications for the woman and baby.
Roberts stressed the latest findings do not mean that pregnant women should not take their prenatal vitamins, which contain much lower doses of vitamins C and E.
The study found that other problems such as low birth weight or respiratory distress syndrome, or the need for a Caesarean section, were also unaffected by the daily dose of 1,000 mg of vitamin C or 400 International Units of vitamin E.
The study, reported in the New England Journal of Medicine, was undertaken because an earlier test of 283 women found that the two vitamins reduced the risk of preeclampsia -- a major cause of death among pregnant women in developing countries -- by 60 percent.
But the result has been controversial because other tests failed to support that original finding, perhaps because only 17 percent of the women in the original study were taking prenatal vitamins.
In subsequent tests, 70 percent were already taking prenatal vitamins.
Roberts said two other large-scale tests of the vitamins have also suggested that the vitamins may actually contribute to hypertension.
It clearly looks like the finding is real based on the three studies, he said.
Vitamins, however, play other roles in protecting from disease.
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, Dr. Catherine Spong of the National Institute of Child Health and Human Development, which helped pay for the study, said in a statement.
In our study, participants took supplements containing higher doses of vitamins C and E -- about 10 times the amount in typical prenatal vitamins -- in addition to any pregnancy vitamins they may have been taking.
In the United States, preeclampsia is present in 15 percent of premature births and can affect both the mother and the fetus.