Pregnant women with epilepsy, particularly those on anti-seizure medications, may have higher rates of cesarean section and heavy bleeding after delivery than other women, a new study finds.

The increased odds are small, researchers stress, and in general, women with epilepsy have a low rate of complications during labor and delivery. Nor should pregnant women on anti-epilepsy drugs interpret the findings as an indication they should stop their medication.

But the findings, reported in the obstetrics journal BJOG, add to evidence that women with epilepsy tend to have more pregnancy-related problems than women without the disorder.

It's estimated that more than 90 percent of pregnant women with epilepsy deliver a healthy baby, according to the Epilepsy Foundation of America.

However, these women do generally have higher risks of certain pregnancy complications, like vaginal bleeding, anemia, preterm birth and preeclampsia -- a disorder marked by high blood pressure and protein buildup in the urine, due to stress on the kidneys.

Studies have come to conflicting conclusions as to whether women with epilepsy have higher risks of complications related to labor and delivery -- such as a greater need for labor induction, instrument-assisted delivery or C-section, or a higher risk of heavy bleeding.

But many of those studies have been relatively small and hospital-based (rather than using data from women in the general population).

So for the new study, researchers used Norway's national birth registry to analyze information on more than 365,000 women who gave birth between 1999 and 2005. A total of 2,805 of those women, or 0.8 percent, had epilepsy or a history of it.

Overall, the data showed that the majority of women with epilepsy have a low risk of complications during labor and delivery, and can deliver vaginally, lead researcher Dr. Ingrid Borthen, of the University of Bergen in Norway, told Reuters Health in an email.

Still, they did have increased risks of C-section, particularly planned ones. And women on anti-epilepsy drugs had higher rates of requiring labor induction and heavy bleeding after giving birth.

Among women without epilepsy, 13 percent had their labor induced, versus 19.5 percent of women on anti-epilepsy drugs. The rate among women not on an anti-epilepsy drug was 14 percent -- which was not statistically different from women without epilepsy.

When it came to C-section, 14 percent of women without epilepsy had the procedure -- either planned or unplanned -- versus 18 percent of women with epilepsy who were not on anti-epilepsy drugs, and 21 percent of those who were on the drugs.

Epilepsy was particularly linked to a higher risk of planned C-section, compared with women without the disorder. The odds were 50 percent greater for women not on anti-epilepsy drugs, and 90 percent greater for women on the drugs when other factors -- like the woman's age and childbirth history -- were taken into account.

Heavy bleeding after birth, meanwhile, was also more common among women on anti-epilepsy drugs -- affecting 19 percent, compared with just under 14 percent of women without epilepsy.

In the case of such postpartum bleeding, the epilepsy medications may be a cause, according to the researchers.

Anti-epilepsy drugs, they note, are associated with vaginal bleeding during pregnancy, possibly related to their propensity for causing folate deficiency or their effects on vitamin K, which is involved in blood clotting.

It is not clear, though, why women on anti-epilepsy drugs had particularly elevated rates of labor induction and C-section, according to Borthen. It could be related to the fact that women who stayed on anti-epilepsy drugs during pregnancy likely had more-severe epilepsy than women who were not on the medications.

Epilepsy itself is not an indication for labor induction, Borthen said, and the increased rate was not explained by relatively higher rates of pregnancy complications among women with epilepsy. Similarly, such complications did not explain the increased C-section rates among both women on anti-epilepsy drugs and those not on the drugs.

It's possible, according to Borthen, that women with poorer seizure control during pregnancy were more likely to have a labor induction or C-section. But the researchers lacked the information to study that question.

The findings build on recent evidence that women with epilepsy may, in fact, have somewhat higher risks of C-section and labor induction, according to Dr. Page B. Pennell of Brigham & Women's Hospital and Harvard Medical School in Boston, who was not involved in the study.

Now the question for researchers is why, said Pennell, who is also chair of the professional advisory board for the Epilepsy Foundation.

One possibility, she told Reuters Health in an interview, is that obstetricians are more likely to plan an induction or C-section for a woman with epilepsy, particularly a woman with more-severe epilepsy. They might, for example, worry that these women will have seizures during spontaneous labor and delivery -- even though, research suggests, this happens to less than 2 percent of women.

The bottom line for women with epilepsy, according to Pennell, is that the excess risks of labor induction, C-section and heavy bleeding after birth appear relatively small.

And for women on anti-epilepsy drugs, she said, this should in no way be taken to mean that they should stop taking their medication.

It is not clear how well the current findings can be extrapolated to countries other than Norway, as obstetric practices can vary widely from nation to nation.

Norway, Borthen noted, has a fairly low C-section rate, as exemplified by the 14 percent rate among women without epilepsy. In the U.S., by contrast, about one-third of all deliveries are done C-section.

The generally low rate in Norway, according to Borthen, made it easier for this study to demonstrate a difference associated with epilepsy.