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Seizure Disorders in Pregnancy

By Lara A. Friel, MD, PhD, Associate Professor, Maternal-Fetal Medicine Division, Department of Obstetrics, Gynecology, and Reproductive Sciences, University of Texas Health Medical School at Houston, McGovern Medical School

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Seizure disorders may impair fertility. But certain anticonvulsants may make oral contraceptives less effective, resulting in unintentional pregnancy.

The dose of anticonvulsant drugs may have to be increased during pregnancy to maintain therapeutic levels. If women get enough sleep and anticonvulsant levels are kept in the therapeutic range, seizure frequency does not usually increase during pregnancy, and pregnancy outcome is good; however, risks of preeclampsia, fetal growth restriction, and stillbirth are slightly increased.

Generally, uncontrolled seizures are more harmful during pregnancy than is use of anticonvulsants; thus, the top priority of treatment during pregnancy is to control seizures. Preconception consultation with a neurologist is recommended to stabilize maternal seizures before pregnancy. Clinicians should use the lowest possible dose of anticonvulsants and as few different anticonvulsants as possible.

Congenital malformations are more frequent in the fetuses of women with a seizure disorder (6 to 8%) than in fetuses of women in the general population (2 to 3%). Risk of intellectual disability may also be increased. These risks may be related to the seizure disorder as well as anticonvulsant use. Risk of hemorrhagic disease of the newborn (erythroblastosis neonatorum) may be increased by in utero exposure to certain anticonvulsants (eg, phenytoin, carbamazepine, phenobarbital); however, if prenatal vitamins with vitamin D are taken and vitamin K is given to the neonate, hemorrhagic disease is rare.

Taken during pregnancy, phenobarbital may reduce the physiologic jaundice neonates commonly have, perhaps because the drug induces neonatal hepatic conjugating enzymes. Phenytoin is generally preferred.

All anticonvulsants increase the need for supplemental folic acid; 4 mg po is given once/day. Ideally, it is started before conception.

Vaginal delivery is usually preferred, but if women have repeated seizures during labor, cesarean delivery is indicated.

Anticonvulsant levels can rapidly change postpartum and should be closely monitored then.