US researchers found that women who took an epilepsy drug valproate, also known as Epilim in the UK, during their pregnancy risked giving birth to children with a lower IQ or with mental retardation.

Currently, around 140 British families claim that the drug has damaged their children. Many of the children whose mothers took valproate during their pregnancies are suffering from fetal anti-convulsant syndrome and have neural, behavioral and physical disorders such as cleft palate and spina bifida, learning difficulties, and abnormalities in movement, speech, vision and hearing.

Researchers compared the IQ results of 187 children born to mothers who had taken the epilepsy drugs carbamazepine, lamotrigine, phenytoin, or valproate during pregnancy. Around 24 % of the children of mothers who took valproate had an IQ low enough to be defined as mentally retarded, compared to 12 % for carbamazepine and phenytoin and 9 % for lamotrigine. These findings support other studies that have shown valproate poses an increased risk for fetal death and birth defects.

Patients should be advised about the risks associated with valproate especially in women of child bearing potential. However, the drug should not be stopped without doctor’s orders as such behaviours could result in seizures and even death.