Absence seizures, simple partial seizures, and complex partial seizures during pregnancy pose no danger to the fetus unless the woman injures herself during the seizure, which is rare. Convulsive (tonic-clonic) seizures in the woman, however, can be dangerous for the developing fetus. Most women who have one or two tonic-clonic seizures during pregnancy have healthy babies, but during a convulsion, there is a risk of trauma to the abdomen, potentially injuring the baby. Also, the temporary interruption of breathing that accompanies tonic-clonic seizures, which is rarely of any significance for the woman, can lead to oxygen deprivation for the fetus, whose heart rate slows for as much as 30 minutes after a tonic-clonic seizure. The greatest dangers are prolonged or repetitive tonic-clonic seizures, which can seriously impair the supply of oxygen to the fetus’s brain and other organs. Tonic-clonic seizures are probably most dangerous to the fetus during the last trimester, when the brain is larger and needs more oxygen.