text: The use of Zonegran (zonisamide) by pregnant women hasn't been fully studied, but there are serious concerns based on studies using animals. When it was given to pregnant mice, rats, and dogs early in pregnancy, there were high rates of fetal abnormalities, especially heart defects and skeletal malformations. After it was given to monkeys during certain stages of pregnancy, many of the fetuses died, possibly because of malformations. All of these effects occurred at doses (and blood levels in the mother) that were equivalent to the amounts used to treat epilepsy in humans, or sometimes even lower. There was also a higher rate of death among the offspring of rats who were given zonisamide late in their pregnancy. The U.S. Food and Drug Administration (FDA) has labeled Zonegran as "Pregnancy Category C" and recommends that women who could possibly become pregnant should use effective birth control while using Zonegran. Recognizing that seizures in the mother also may be hazardous to a fetus, however, they conclude that the risks and benefits must be weighed in considering the use of Zonegran during pregnancy. Tell your doctor right away if you are pregnant or thinking about becoming pregnant.