Phenytoin is a medication used to treat epilepsy (seizure disorder). If phenytoin is taken by the mother in the first trimester, there is approximately a 5 to 10 percent chance that the baby could be born with a combination of birth defects known as the Fetal Hydantoin Syndrome. Babies with this syndrome may be born with some of the following health problems:
Certain facial characteristics
Abnormalities of the fingers and nails
Phenytoin crosses the placenta in such a way that the developing fetus receives a much higher dose of the medication than the mother is taking (the drug is metabolized differently by the fetus). This is especially true when the medication is used during the first trimester of pregnancy.
Despite these risks, seizure control during pregnancy is very important. Therefore, when a woman with epilepsy is planning a pregnancy, it is important for her to meet with both her neurologist and her obstetrician, before conception, to discuss the specific treatment to be used to control seizures while pregnant.