In the United States, the Food and Drug Administration (FDA) assigns each medication to a "Pregnancy Category" according to whether it has been proven to be harmful in pregnancy. Zarontin is listed in Pregnancy Category C. This means that women should be cautious, but sometimes the benefits may outweigh the risks. In fact, a large majority of women who use Zarontin during pregnancy have normal, healthy babies.

All women who are capable of becoming pregnant should take at least 0.4 mg (400 mcg) of the vitamin called folic acid every day because it helps to prevent one type of birth defect. (The most well-known of these is spina bifida, in which the spinal cord is not completely enclosed.) If the doctor thinks a woman is at especially high risk, a much larger dose of folic acid—4 mg (4000 mcg) per day—may be recommended, beginning before the woman becomes pregnant.

Women with epilepsy who are pregnant or thinking about becoming pregnant should talk to their doctor about their seizure medicines. Taking more than one seizure medicine may increase the risk of birth defects, so doctors sometimes gradually reduce the number or amount of seizure medicines taken by women planning for pregnancy. This is not done routinely, however, because it increases the risk of seizures. Some kinds of seizures can injure the baby, so women should not stop using seizure medicines or reduce the amount they take without their doctor's OK.

About 20% to 35% of women have seizures more often during pregnancy because of changes in hormones or changes in how their seizure medicine is handled by the body. It is helpful for the doctor to check the levels of medicine in the blood regularly during pregnancy so that the dosage can be adjusted if necessary.

Women taking Zarontin who are interested in breast-feeding their baby should talk to their doctor, because this medicine does pass through breast milk.