The research recommends that mums-to-be need to be fully informed of the risks of treatment, but these should be weighed against the need for effective seizure control during pregnancy, say the researchers.
Several studies indicate that epilepsy drugs, particularly sodium valproate, taken during pregnancy, are associated with neurodevelopmental disorders, but few of these studies have been based on real-life population circumstances (population data).
To address this, the researchers from the Neurology Research Group in Swansea University Medical School used routinely-collected healthcare data from the Secure Anonymous Information Linkage (SAIL) databank and national school test (key stage 1) data to compare the academic performance of 7-year-olds in Wales born to mothers with epilepsy.
SAIL contains the anonymised primary care health records of 80 percent of Welsh family doctors, corresponding to around 77 percent of the Welsh population (2.3 million people).
The Key Stage 1 (KS1) test assesses maths, language (English/Welsh) and science among 7-year-olds, scoring them from levels 1 to 3. Test results were available for 440 children whose mums had been diagnosed with epilepsy before their pregnancy for 2003 through to 2008.
Prescription patterns were divided into five categories: treatment with one drug (carbamazepine, lamotrigine or sodium valproate); a combination of several drugs; and no drug treatment. Twenty (54%) of the 39 mums prescribed several drugs were taking sodium valproate, but there were 15 different drug combinations in all.
The results showed that children born to mothers, who had been prescribed carbamazepine or lamotrigine, or nothing, performed just as well as those born to mums of the same age and deprivation level, but without epilepsy (comparison group).
But those whose mothers had been prescribed sodium valproate during their pregnancy performed 10.5 - 13 per cent less well on all KSI tests than those in the comparison group.
Children born to mums who had been prescribed a combination of epilepsy drugs achieved worse results still. Their scores were 19-22 percent lower. Also, excluding children with epilepsy and whose mothers smoked from the analysis didn't materially change the results.
The researchers acknowledge that they weren't able to account for certain potentially influential factors, such as the mothers' IQ, weight or alcohol consumption; the doses of epilepsy drugs prescribed; or intake of folic acid around conception.
But their results echo those of other independent studies, they point out.
Professor Mark Rees, Professor of Neurology and Molecular Neuroscience Research said, "While this study highlights the risk of cognitive effects in the children of mothers prescribed sodium valproate or multiple [anti-epilepsy drugs], it is important to acknowledge that some epilepsies are difficult to manage without these treatment regimens."
The findings appear in the Journal of Neurology, Neurosurgery, and Psychiatry. (ANI)