The RDA for pregnant women is 18 mg of Vitamin E. Recent studies have shown that taking in too much Vitamin E during pregnancy can cause birth defects in children. Specifically, too much Vitamin E has been shown to cause heart defects in children after birth.

The study of Vitamin E was released in the International Journal of Obstetrics and Gynecology in February of 2009. According to the study, pregnant mothers who consumed high levels of Vitamin E were 70% more likely to have children with birth defects.
In addition to the birth defects, children born to mothers who ate diets high in Vitamin E and added a supplement on top of their diets were up to 9 times more likely to have congenital heart defects.
Vitamin E is a strong antioxidant and while the positive effects of antioxidants on the body are well researched, the supplemental Vitamin E plus high dietary levels of Vitamin E in the pregnant diet is thought to disturb the healthy balance of oxidants and antioxidants.
Doctors and researchers are not completely sure how the extra Vitamin E causes these heart problems, but it is safer to err on the side of caution than risk a heart defect. The maximum amount of Vitamin E a pregnant mother should consume daily is between 15 and 19 mg. The upper end of the RDA is caved for use by lactating women after birth.
On the flip side of the coin, other research has noted that too little Vitamin E during pregnancy is linked to a higher instance of asthma in babies. This is another reason to watch what you eat and take the prenatal vitamin every day.