Sodium valproate or carbamazepine for psychiatric disorders during pregnancy

Fetal exposure to sodium valproate is associated with a high risk of major congenital malformations (neural tube defects have an incidence of 11% in some studies) and neurodevelopmental disorders (30 to 40% estimated incidence). Do not use sodium valproate in pregnancy for a psychiatric disorder unless other treatment options (eg electroconvulsive therapy [ECT] ) cannot be used and there is a high risk of harm if sodium valproate is stopped (eg relapse to a disabled or suicidal state).

The risk of major congenital malformations associated with antenatal carbamazepine use is of lesser magnitude, but still concerning. The risks with carbamazepine appear to be limited to the first trimester—it may be used from the second trimester.

If a patient taking sodium valproate or carbamazepine becomes pregnant, discuss the risk of fetal malformations and alternative therapies; see Principles of psychotropic use during pregnancy and, if relevant, Considerations in managing bipolar disorder during pregnancy for treatment guidance.

Neural tube defects can usually be detected with routine screening at 13 weeks gestation. A fetal anatomy scan is also offered at 18 to 20 weeks. Encourage a patient who has taken either anticonvulsant in the first trimester to have these tests—refer her to an obstetric service that offers screens for major congenital malformations (eg alpha-fetoprotein measurement, ultrasound examination, fetal echocardiography).

Limited data suggest that high-dose folic acid may reduce the risk of major congenital malformations and is not associated with adverse effects. For patients taking sodium valproate or carbamazepine who are either planning a pregnancy or are pregnant, use:

If stopping either drug or switching to an alternative drug, seek psychiatric advice and review the patient’s mental state every 1 to 2 weeks for the next 4 to 8 weeks for signs of relapse. Ideally, obtain perinatal psychiatrist opinion at least once during the pregnancy.

Vitamin K supplementation during pregnancy is no longer routinely recommended to reduce the risk of haemorrhage in neonates with gestational exposure to enzyme-inducing antiepileptics (eg carbamazepine); instead, ensure the neonate receives intramuscular vitamin K immediately after birth.