A study on the potential risks of epilepsy medication in pregnancy revealed on Wednesday that a drug found to affect the cognitive ability of toddlers born to women who took the drug for epilepsy has a longer-term impact on their IQ.
Researchers in the United States carried out follow-up tests among the same group of children whose investigation in 2009 led to warning by the US health watchdog about the potential risks of the drug valproate in pregnancy.
The children -- examined at the age of three -- had below-par cognitive skills, which prompted the US Food and Drug Administration (FDA) to issue a warning about its use in pregnancy.
The new research, published in the journal The Lancet Neurology, examined the same children at the age of six.
Children born to mothers who had used valproate in pregnancy had an IQ that was seven to 10 points lower than children whose mothers had used one of three other epilepsy drugs, it found.
The higher the dose of valproate the mother took in pregnancy, the greater the IQ discrepancy. Verbal skills and memory were also affected.
The study, conducted between October 1999 and February 2004, by Kimford Meador at Emory University in Atlanta, Georgia, covered 305 pregnant women who had been using either valproate, carbamazepine, lamotrigine, or phenytoin.
The first analysis looked at 311 children in the United States and Britain; in the followup at the age of six, it covered 224 of them.
However, the study also suggested that IQ may improve with age for infants exposed to any of these drugs.
And by taking folic acid supplements, expectant mothers may improve IQ scores. This is the first time a boost has been shown in a study of pregnant women with epilepsy.
Valproate is, for some people, the only drug that can control their epilepsy, so the findings on dosage and the beneficial effects of folic acid could be useful.
"Valproate usage during pregnancy has a significant negative effect on children's IQ, which lasts beyond their earliest years. IQ at age six is strongly predictive of adult IQ and school performance, so our research suggests that valproate use during pregnancy is likely to have long-term negative effects on a child's IQ and other cognitive abilities," Meador said.
"For many antiepileptic drugs, there is simply no research available on their effects on women and their children during pregnancy, and given that many women do not have the option of stopping medication during pregnancy, more research in this area is urgently needed."