Women who’ve just become pregnant may want to watch how much vitamin E they take in. It seems that high levels of vitamin E early in pregnancy may increase the risk of the baby being born with a heart defect, according to a Dutch research team.

They studied 276 mothers of children born with heart defects and 324 “control” mothers whose babies were free of heart defects.

When their infants were 16 months old, the mothers completed food frequency questionnaires for the 4 weeks prior to the study. According to the researchers, dietary patterns during this time are similar to those before the women became pregnant.

The likelihood of having a baby with a heart defect was 70 percent higher for women with the highest vitamin E intake from diet alone, compared to those with the lowest intake, the investigators found.

Moreover, high dietary vitamin E intake plus the use of a supplement containing vitamin E increased the risk of congenital heart defects 5- to 9-fold, Dr. R. P. M. Steegers-Theunissen at University Medical Center, Rotterdam, and colleagues report in BJOG: An International Journal of Obstetrics and Gynaecology.

The researchers point out that high levels of vitamin E “may imbalance the oxidant/antioxidant state” in embryonic tissues.

Other possible mechanisms for the adverse effects of high vitamin E on the baby, they say, include modification of genes involved in embryonic heart development and inhibition of cellular enzymes involved in clearing away naturally occurring toxins.

SOURCE: BJOG: An International Journal of Obstetrics and Gynaecology, February 2009.