Chemical Teratogens, Carcinogens, Mutagens
In 1978 valproic acid was approved for use in the US. The drug had been available in Europe for more than a decade before it was available in the US. Valproate has been effective in a wide variety of partial and generalized seizures.
Based on data from the birth defects monitoring system for the Rhone-Aples region of France, an increase in spina bifida in the offspring of mothers who took valproic acid during pregnancy was observed. From this data, the estimated risk of fetal spina bifida for a woman taking valproic acid during the first trimester of pregnancy is 1 - 2%.
This data has been confirmed in subsequent studies. Therefore, valproate exposed fetuses should be monitored for spina bifida and appropriate genetic counseling/prenatal diagnosis offered.
It has also been suggested through other studies that a "Fetal Valproate Syndrome" exists. The features described include facial dysmorphism, limb/neural tube/cardiac defects, and developmental delays.