Merck Manual

Please confirm that you are a health care professional

honeypot link

Seizure Disorders in Pregnancy


Lara A. Friel

, MD, PhD, University of Texas Health Medical School at Houston, McGovern Medical School

Last full review/revision Apr 2020| Content last modified Apr 2020
Click here for Patient Education

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

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

Generally, uncontrolled seizures are more harmful during pregnancy than is use of antiseizure drugs; 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 antiseizure drugs and as few different antiseizure drugs 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 use of antiseizure drugs. Risk of hemorrhagic disease of the newborn (erythroblastosis neonatorum) may be increased by in utero exposure to certain antiseizure drugs (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 antiseizure drugs increase the need for supplemental folic acid; 4 mg is given po once/day. Ideally, it is started before conception. Taking folic acid supplements before conception helps reduce risk of neural tube defects.

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

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

Drugs Mentioned In This Article

Drug Name Select Trade
No US brand name
Click here for Patient Education
NOTE: This is the Professional Version. CONSUMERS: Click here for the Consumer Version
Professionals also read

Also of Interest

Download the Manuals App iOS ANDROID
Download the Manuals App iOS ANDROID
Download the Manuals App iOS ANDROID