Any mother will tell you: Yes, it hurts. A lot. Like nothing else. Which is why the epidural seems like a very good idea, although doctors have long thought that starting an epidural early increases the risk that a woman will need a cesarean section. So researchers at Northwestern University set out to test that belief.

What the researchers wanted to know: Does getting an epidural early in labor increase the risk of cesarean delivery?

What they did: Healthy women who showed up at Prentice Women's Hospital in Chicago in labor were invited to participate in the study if they wanted to get an epidural. Women were excluded if they'd had induced labor or if they'd already dilated to 4 centimeters or greater. Then, when they asked for pain relief, they were randomly assigned either to get an epidural or to get systemic analgesia, which was a combination of intravenous and intramuscular doses of the pain drug hydromorphone. Most of the women who originally got hydromorphone were eventually given an epidural. (Which was fine, because the researchers were looking at the effect of giving an epidural early, before the cervix had made it to 4 cm.) The study included 728 women.

What they found: The women who got epidurals early in labor were no more likely to have cesareans. They weren't any more likely to need instruments for a vaginal delivery, either. Here's something else interesting: for women who had vaginal deliveries, the time from their first dose of pain medication to the birth was shorter if that first dose was an epidural. A lot shorter—the median time was 398 minutes for an epidural and 479 minutes if the first dose was the systemic pain relief. Women who had epidurals were also in less pain and were less likely to throw up than women who had the systemic pain relief.

What the study means to you: Just like that, the argument for holding off on the epidural until later in labor has a major hole poked in it. It's amazing what a little scientific experimentation will do. The fact remains that people have observed in the past that women who had epidurals early were more likely to have cesarean sections, but the researchers have a plausible explanation: Maybe women who ask for an early epidural are asking because they're in more pain and are already at a higher risk of cesarean sections.

Caveats: There weren't enough women in the study to detect a small increase in the rate of cesarean sections, but it could be argued that a small difference isn't particularly important. Also, the women in this study were having their first babies and had spontaneous labor or spontaneous rupture of the membranes; the same may not be true of women who are on their second pregnancy or who have had labor induced.

Find out more: The American College of Obstetricians and Gynecologists is of the opinion that if a woman in labor wants pain relief, you should give her pain relief.

Read the article: Wong, C.A. et al. "The Risk of Cesarean Delivery With Neuraxial Analgesia Given Early Versus Late in Labor." New England Journal of Medicine. Feb. 17, 2005, Vol. 352, No. 7, pp. 655–665.

Abstract online: http://content.nejm.org