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Women now spend nearly three hours longer in labour than they did 50 years ago, according to a new study.

Researchers at the U.S. National Institutes of Health suggested the longer delivery times might be due to the fact that the use of epidural anesthesia is much more common today than it was a generation ago.

The study compared data from nearly 40,000 deliveries between 1959 and 1966 with data from nearly 100,000 deliveries between 2002 and 2008.

According to that analysis, the first stage of labour – when the cervix dilates but before active pushing – had increased 2.6 hours for first-time mothers. For mothers who had previously given birth the first stage of labour took two hours longer.

The study also found several other key differences between childbirth in the 2000s and childbirth in the early 1960s: Infants born in the new millennium were born five days earlier, on average, and also weighed more. Women also weighed more, with an average body mass index before pregnancy of 24.9, compared with 23 for women in the earlier group. As well, women in the latter group were four years older, on average, than were women in the 1960s.

"Older mothers tend to take longer to give birth than do younger mothers," the study's lead author, S. Katherine Laughon, M.D., of the Epidemiology Branch of the Eunice Kennedy Shriver National Institute of Child Health and Human Development, said in a release. "But when we take maternal age into account, it doesn't completely explain the difference in labour times."

Changes in delivery practices – specifically when it comes to pain management – might help explain the difference in labour times, the study suggests. Epidurals, which relieve pain but often make it harder to push, were used in more than half of deliveries in the latter group, compared to only four per cent of deliveries in the 1960s.

At the same time, however, the hormone oxytocin, which is given to speed up labour, was administered in 31 per cent of deliveries in the early 2000s compared to just 12 per cent in the 1960s.

"Without it, labour might even be longer in current obstetrics than what we found," Dr. Laughon said.

The study also found cesarean delivery accounted for 12 per cent of deliveries in the early 2000s, four times higher than it was 50 years ago.

The authors of the study, published in the American Journal of Obstetrics & Gynecology, called for further research to investigate if and how modern delivery practices might be making the time labour takes longer.

Does it worry you that today's labours are taking longer on average than those in the 1960s?

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