Women who use Topamax should know that they can’t rely on hormonal birth control if they are of childbearing age. That’s because Topamax and other anticonvulsant drugs can increase the metabolism of estrogen and progesterone, leading to failure of hormone-based birth control.
According to some studies, among women who take Topamax and birth control pills, the rate of contraceptive failure could be as high as 7 percent. This is important, because taking Topamax during pregnancy increases the chances that a baby will be born with an oral cleft. The U.S. Food & Drug Administration (FDA) has also received reports of other birth defects in children born to women who took Topamax during pregnancy.
According to that database, there have been over 100 reports of possible Topamax birth defects, including 29 oral clefts, 29 limb malformations, 27 heart defects, 26 reports of other congenital defects, 23 cranio-facial defects, 15 reports of spina bifida/spinal malformations, and 5 reports of persistent pulmonary hypertension of the newborn (PPHN).
In March, the FDA moved Topamax from Pregnancy Category C to Pregnancy Category D, a classification that means there is positive evidence of human fetal risk based on human data. The FDA made this decision after data from the North American Antiepileptic Drug (AED) Pregnancy Registry indicated that infants exposed to Topamax as a single therapy during the first trimester of were more likely to be born with an oral cleft – cleft lip or cleft palate.
Certain birth defects, such as oral clefts, are known to develop during the first trimester of pregnancy, before most women even know they are expecting. For that reason, women of child bearing age who take Topamax are advised to use additional forms of birth control – such as condoms, copper IUD, sponge or spermicides – to safeguard against birth control pill failure.