March 25, 2005

Anticonvulsant drug may pose greater birth-defect risk

Use of the anticonvulsant drug valproate during pregnancy may carry a greater risk of birth defects than do other antiseizure medications. In the March 22 issue of Neurology, researchers from the North American AED (Antiepileptic Drug) Pregnancy Registry at the MGH report that women taking valproate alone had four times greater risk of having a child with a major malformation than did women taking other drugs. "The basic message for women who take valproate is to plan ahead if they want to have children," says Lewis Holmes, MD, chief of the Genetics and Teratology Unit at MassGeneral Hospital for Children, director of the registry and senior author of the report. "Discuss the risks with their physician and consider taking alternative drugs."

Valproate is used to treat seizures, migraines and such psychiatric disorders as bipolar disorder. Earlier studies suggested a potential risk of birth defects and primarily neural tube defects such as spina bifida, but none had definitively established the level of risk and the types of malformations that most frequently occur. The current study analyzed information from 149 women who took only valproate while pregnant. Of those 149 women, 16 had infants with major birth defects. Three infants had spina bifida, and a wide variety of malformations was seen in the others, including developmental delays.

"This is the first indication to many neurologists that they should focus on more than the risk of spina bifida with this drug," says Holmes. "The women in our study who had children with spina bifida or other malformations had all taken the dose of folic acid recommended to prevent neural tube defects." The North American AED Pregnancy Registry was established in 1996 and has enrolled more than 4,000 women who took anticonvulsant drugs during pregnancy. It is the largest hospital-based pregnancy registry of any kind. Caitlin Reilly Smith, MPH, of the registry is a co-author of the report.