Women who must take insulin daily to control their blood sugar are three or four times more likely to have a baby with major birth defects than are other mothers. That's not to say they should abandon insulin, however. Without it, many diabetic women and their babies wouldn't survive pregnancy at all. Birth defects among diabetics can be greatly reduced if women get their blood sugar levels under control before becoming pregnant and strictly manage their diets throughout pregnancy. Gestational diabetes, which develops during pregnancy, can also be harmful to mother and child, but it can be controlled through diet or medication.
Epilepsy also increases a woman's chance of having a baby with a birth defect.
It's not clear whether the disease itself or the drugs used to control it cause malformations, but in either case, the woman's neurologist and obstetrician should work together to find the safest course of treatment for the epilepsy and pregnancy. Rubella, toxoplasmosis, cytomegalovirus, and syphilis can cause birth defects in the infants of women who have these infectious diseases. Rubella infection during early pregnancy can cause abnormalities of the heart, eyes and ears. Any woman planning a pregnancy should be tested for rubella immunity and vaccinated if necessary. She must wait three months after vaccination before becoming pregnant, however, because the vaccine itself can endanger a developing fetus.