TUESDAY, May 17 (HealthDay News) -- Newer epilepsy medications don't increase the risk of major birth defects in women taking these drugs during the first trimester of pregnancy, according to new research.

But because the drugs are relatively new, further studies are needed to get a clearer picture of their safety profile, experts said.

In a large study of children born in Denmark, including those exposed to newer anti-epileptic drugs, researchers found the rate of major birth defects was 3.2 percent for babies born to women taking the epilepsy medications and 2.4 percent for women not taking these drugs.

"In a nationwide Danish study of more than 800,000 births, we found no support for an increased risk of birth defects following use of newer generation anti-epileptics in early pregnancy," said the study's lead author, Ditte Molgaard-Nielsen, an epidemiologist at Statens Serum Institute in Copenhagen.

"Pregnant women and women planning pregnancy can be reassured that our study and current knowledge of the safety of newer generation anti-epileptics does not provide cause for concern with respect to birth defect risk," she added.

Results of the study were published in the May 18 issue of the Journal of the American Medical Association.

Between 0.2 percent and 0.5 percent of pregnant women take anti-epileptic medications during pregnancy, according to background information in the study. Most women who take these medications do so to control seizures, but sometimes the drugs are prescribed for bipolar mood disorders, migraines and nerve pain disorders, the study authors noted.

When used during pregnancy, older epilepsy medications -- such as phenobarbital, phenytoin, valproate and carbamazepine -- have been linked to as much as a three-fold higher risk of birth defects, according to the study.

The difficulty in managing women with epilepsy during pregnancy is that treatment needs to be individualized, and not all women respond to all treatments. In many cases, it takes more than one medication to control seizures. And, uncontrolled epilepsy can also cause harm to a fetus, according to Dr. Loralei Thornburg, a maternal-fetal medicine specialist at the University of Rochester's Strong Memorial Hospital in New York, who was not involved with the study.

Medication options for women with epilepsy increased in the 1990s, but because these drugs are relatively new, little information has been available about their potential risk in pregnant women, the authors of the new study pointed out.

For the current study, Molgaard-Nielsen and a colleague reviewed data on all live births in Denmark from January 1996 through September 2008. The study included a total of 837,795 live births, including 1,532 babies who were exposed to newer epilepsy medications during the first trimester of pregnancy.

In the group of babies exposed to newer medications, such as lamotrigine, oxcarbazepine, topiramate, gabapentin and levetiracetam, 49 (3.2 percent) were diagnosed with major birth defects. In the large group of babies who weren't exposed to epilepsy medications, 19,911 babies (2.4 percent) were diagnosed with a major birth defect, according to the report.

Although the overall rates of birth defects were low, the study authors found that babies exposed to topiramate had 44 percent higher odds of having a birth defect, while babies exposed to lamotrigine during the first trimester of pregnancy had 18 percent higher odds of a birth defect. Those exposed to oxcarbazepine had 14 percent lower odds of a birth defect, the results showed.

There weren't enough women taking gabapentin or levetiracetam to estimate whether or not these medications are associated with increased odds of birth defects, the study authors noted.

"The management of epilepsy is complicated and challenging, and should be directed by experienced clinicians taking into account a wide range of factors, not just birth defect risks. These adverse effects include preterm birth, low birth weight, fetal death and adverse effects experienced by the mother," said Molgaard-Nielsen.

Still, Molgaard-Nielsen added: "Further studies investigating newer-generation anti-epileptic drugs and the risk of adverse effects other than birth defects are needed to provide a more complete picture of the risks and benefits of different anti-epileptics."

Thornburg added: "This is the best evidence we have thus far to say these drugs are safer than previous medications. Are they absolutely safe? I don't think anyone can say that about any medication, but it's about what's the best choice."

More information

Learn more about epilepsy and pregnancy from the Epilepsy Foundation.