Around 20,000 babies have been born with disabilities in the UK alone after their mothers took the drug, Epilim (sodium valproate), since it came on the market in 1973.
Babies in the womb have a 10 per cent chance of developing physical abnormalities, and a 40 per cent risk of cognitive problems such as learning difficulties or autism, if exposed to valproate medications.
The manufacturer, Sanofi, and the drug regulators concealed the risks because they didn't want to cause "fruitless anxiety", a European Medicines Agency hearing has been told.
The regulator, the Committee on Safety of Medicines, did send a letter to doctors, warning that the drug could harm the fetus, but decided the warning shouldn't go on the package inserts that came with the drug "so there would be no danger of patients themselves seeing it".
Women are still unaware of the dangers of taking sodium valproate when they are pregnant. A survey among 2,000 women with epilepsy last month revealed that 68 per cent didn't know, even though the Medicines and Healthcare Products Regulatory Agency—which replaced the Committee on Safety of Medicines—produced a 'toolkit' last year.