The U.S. Food and Drug Administration (FDA) lists Topamax in Pregnancy Category C. This indicates that caution is advised, but the benefits of the medication may outweigh the potential risks. There have not been enough well-controlled studies in women, but studies in animals have shown some harm to the fetus.

The babies of women taking seizure medicines have a greater than usual number of major birth defects like cleft lip, cleft palate, and heart malformations. Defects like these occur in 2-3% of all pregnancies but affect 4-7% of the babies of women taking AEDs. Whether this is also true for Topamax is not yet known. The risk of birth defects is higher for women who take more than one AED and for women with a family history of birth defects.

Advise women who are capable of becoming pregnant to take at least 400 mcg (0.4 mg) of folic acid (folate) daily to help prevent neural tube defects. Women at high risk, such as those with a history of a neural tube defect in a previous pregnancy, should take 4000 mcg (4 mg) daily, beginning before they become pregnant.

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. Whether this applies to Topamax is not known, but it is advisable to check blood levels regularly during pregnancy so that the dosage can be adjusted as needed.

Some Topamax will probably appear in the milk of nursing mothers who take it, yet there is limited information on how much topiramate is passed through breast milk. The potential for seious side effects in nursing infants is unknown. See the package insert for more details.