Valproic acid-induced congenital malformations: Clinical and experimental observations

With a large number of epileptic women being in the childbearing age group, complications of pregnancy in epileptic patients are of concern. Epileptic women are treated with antiepileptic drugs (AED) whether they are pregnant or not. Contrary to prevailing opinion, recent data suggest that epilepsy per se contributes significantly to birth defects possibly because of the same genetic susceptibility that predisposes to epilepsy. Many of these defects closely resemble those attributed to exposure to AED. The syndromes attributed to various AED also considerably overlap with each other. Valproic acid (VPA) induces several minor and major malformations. The relative risk for spina bifida in VPA exposed pregnancies is nearly 20 times higher than that for the general population and about 10 times higher than that attributed to other anticonvulsants. Fetuses of experimental animals treated with VPA during pregnancy exhibit exencephaly unlike the human offspring in whom VPA induces spina bifida. The cranial and spinal malformations observed in humans and laboratory animals indicate that VPA has a preferentially deleterious effect on the neural crest. Several AEDs including VPA tend to lower maternal plasma folate levels. In view of the beneficial effects of periconceptional folate supplementation in prevention of neural tube defects (NTD), future research should be directed at the role of folate in the possible alleviation of VPA-induced NTD. It is also necessary to continue prospective studies to monitor the old and new AED prescribed and to evaluate the role of interactions between drugs used in combinations.