French drug regulators announced on Thursday that medicinal salt valproate was responsible for "severe malformations" in 2,150 to 4,100 children from 1967 to 2016.
According to a study conducted by French drug authority ANSM, women taking valproate during pregnancy were four times more likely to bear children with congenital malformations including spinal deformities, heart disease and genital organ defects.
Valproate is also believed to cause slow neurological development leading to autism and mental problems.
The medication is marketed around the world under brand names such as Depakine, Depakote, Absenor, Convulex,Depakene, Depalept, Deprakine, Encorate, Epival, Epilim, Stavzor,Valcote, Valpakine, as well as other trade names.
The ANSM is to publish a follow-up report on valproate’s neurological effects in the second half of 2017.
The risk of birth defects linked to valproate has been known since the 1980s, especially for spina bifida, which occurs 20 times more frequently in fetuses exposed to the medication.
An earlier estimate suggested that 30 to 40 percent of children exposed in the womb could suffer such disorders.
"The risk of severe malformation is limited to the first two trimesters of pregnancy," said Alain Weil, a researcher at the French health insurance administration and a co-author of the report.
“The study confirms the highly teratogenic [capable of causing birth defects] nature of valproate,” said Mahmoud Zureik, ANSM’s scientific director and co-author of the report.
Some families of children with birth defects born to women who took the drug while pregnant have sued for not being adequately warned about the risks of taking the drug.
Valproate is prescribed for people suffering from epilepsy, bipolar disorder and migraine headaches.