What are the birth defect risks from Topomax?

According to the FDA, topiramate increases the risk of cleft lip or cleft palate (oral clefts) in the babies of pregnant women who take the drug.

The North American Antiepileptic Drug (NAAED) Pregnancy Registry reported evidence of an increased risk of oral clefts in infants exposed to topiramate alone during the first trimester of pregnancy. The oral clefts occurred 1.4 percent of the time compared to a prevalence of 0.38 to 0.55 percent of the time in infants whose mothers took other antiepileptic drugs. There was an oral cleft prevalence of 0.07 percent among infants born to mothers who did not have epilepsy and did not take an antiepileptic medication.

The UK Epilepsy and Pregnancy Register reported a similar increased prevalence of oral clefts (3.2 percent) among infants exposed to topiramate alone, or a 16-fold increase in risk compared to the risk in their background population (0.2 percent), the FDA says.