The U.S. Food and Drug Administration issued a warning on Monday advised pregnant women not to use valproate sodium products for the prevention of migraine headaches. The FDA said a recent study has found the medication could cause decreased IQ scores in children whose mothers took the medication during pregnancy. "Valproate medications should never be used in pregnant women for the prevention of migraine headaches because we have even more data now that show the risks to the children outweigh any treatment benefits for this use," Russell Katz, director of the Division of Neurology Products in the FDA's Center for Drug Evaluation and Research, said in a statement. Women who can become pregnant should not use valproate unless it is essential to managing their medical condition, the FDA said, adding that it's working with the manufacturers to make changes to the drug labels to reflect this new information. This is the second time the FDA has warned on valproate products. In June 2011, the FDA released interim results of a study that showed reduced cognitive test scores in these valproate- exposed children at age 3.