A drug used to treat epilepsy could triple the risk of birth defects, a study suggests.

Researchers at the University of Ulster in the UK found that taking valproic acid in the first trimester increased the risk of malformations at birth.

The study identified seven types of birth defects, including spina bifida, cleft palate, heart defects and limb reduction.

Professor Helen Dolk, a member the university’s Nursing Research Institute and one of the study’s lead researchers, said that expectant mothers who took the drug could increase the risk of birth defects by two to three times.

“Our study has shown that risk varies according to the specific type of malformation and identified seven different types of malformation in which the risk was increased between two and 12 times compared with no anti-epileptic drug use,” she said.

The research used data from about four million births, including live births, stillbirths or terminations with malformations, in 14 European countries between 1995 and 2005.

Ulster researchers worked jointly with the University of Groningen in the Netherlands and the EUROCAT network to carry out the research.