Antiepileptic drug teratogenesis: what are the risks for congenital malformations and adverse cognitive outcomes?

Antiepileptic drug (AED) exposure in utero has been associated with major congenital malformations (MCMs) and adverse cognitive outcomes in the offspring of women with epilepsy (WWE). However, determining the exact risk and the relative risks of AEDs for these outcomes has been challenging, and only in recent years has improved study designs enabled us to get a clearer picture of the risks. Still, there is a startling lack of information for many of the newer and widely used AEDs. At this point of time, studies clearly show that valproate (VPA) as a part of polytherapy or when used as a monotherapy is associated with an increased risk of MCMs, and that it poses about threefold the risk of carbamazepine (CBZ). It is unclear if any other AEDs studied pose an increased risk of MCM occurrence; in the best available large study the absolute rates of MCMs with other several other AEDs were not different from untreated WWE. The absolute risks have been reported as CBZ 2.2%, lamotrigine (LTG) 3.2%, phenytoin (PHT) 3.7%, untreated WWE 3.5%, with VPA as the outlier at 6.2%. In utero VPA exposure is also associated with a risk of lower verbal intelligence quotient (IQ) in children, at approximately 10 points lower than controls. CBZ appears to pose no risk to cognitive outcome, and there is some evidence that PHT and phenobarbital (PB) may be associated with risk of reduced cognitive outcome. Polytherapy is associated with greater risk than monotherapy for both MCMs and cognitive outcome. Although more information is needed and hopefully will be obtained from ongoing prospective studies, it is clear that WWE taking VPA and planning pregnancy should have a discussion with their physician about considering changing to another AED before pregnancy, if possible.