Taiwanese researchers compared children born to 1,016 women with epilepsy with those born to 8,128 women without epilepsy. During pregnancy, 503 of the women with epilepsy had seizures and 513 did not.

Those who had seizures while pregnant were 36 percent more likely than women who did not have epilepsy to have had a baby that weighed less than 5.5 pounds (considered low birth weight), 63 percent more likely to deliver prematurely (before 37 weeks) and 37 percent more likely to have a baby who was small for gestational age.

In another comparison, women with epilepsy who had seizures during pregnancy were 34 percent more likely to have a baby who was small for gestational age than were women with epilepsy who did not have seizures while pregnant.

The study is in the August issue of Archives of Neurology.

Some earlier studies suggested a link between epilepsy and adverse pregnancy outcomes, but others found no connection.

The findings of the new study "suggest that it is the seizures themselves that seem to contribute greatly to the increased risk of infants being delivered preterm, of low birth weight and small for gestational age," wrote Yi-Hua Chen, of Tai Pei Medical University in Taiwan, and colleagues. "For women who remained seizure-free throughout pregnancy, null or mild risk was identified, compared with unaffected women."

Epileptic seizures can affect pregnancy outcomes in a number of ways. Seizures can cause trauma that ruptures fetal membranes, increasing the risk for infection and early delivery. Or seizures can cause contractions in the uterus that cause tension and acute injury.

The researchers emphasized the need for intervention strategies, such as helping women control seizures for a period of time before pregnancy, assisting them in sleeping better, providing education about the risks of seizures while pregnant and teaching them how to cope with stress.

More information

The Epilepsy Foundation has more about women and epilepsy .