Although valproate's risks of causing defects, and especially spina bifida, have been known since the 1980s, drug regulators have been slow to act, and some of the drug's victims say the manufacturer, Sanofi, has not issued strong warnings.
France's drug regulator, the National Agency for the Safety of Medicines, has reported that between 2,150 and 4,100 children have been born with serious defects, such as spina bifida, and heart and genital problems. The risk of autism and other developmental problems was also higher in women taking the drug while they were pregnant. "The study confirms the high teratogenic (ability to cause birth defects) nature of valproate," says Mahmoud Zureik, the agency's scientific director.
Some families whose children were born with birth defects are suing Sanofi, and are claiming warnings about possible risks were inadequate.
The drugs are prescribed to treat bipolar disorder as well as epilepsy. Women with bipolar were less likely to give birth to a child with defects than a woman with epilepsy, although the risk was still twice as high as someone not taking the drug.