Sodium valproate: what are dangers of epilepsy drug for unborn babies?

Drug used to treat epilepsy and bipolar disorder is being given to pregnant women despite risks, data shows

• MHRA to look into cases of unsafe epilepsy drug being given to pregnant women

The anti-epilepsy drug sodium valproate can cause birth defects, but data has revealed it is still being prescribed to pregnant women in the UK, with concerns also raised that they are not always given information about the risks. But what is the drug, and how big is the problem?