American women today on average are giving birth later in life and taking longer in labor than their counterparts in the 1960s, researchers at the National Institutes of Health reported this week. The researchers said they could not identify all the factors that accounted for the increased labor time, but that changes in delivery room practice probably are a major factor.

The researchers compared data on nearly 140,000 births that took place between 1959-1966 and 2002-2008.

Compared with the earlier generation, women in 2002-2008:

  • Were in labor an average of 2.6 hours longer if it was their first time giving birth and 2 hours longer if they had previously given birth.
  • Were about 4 years older, on average.
  • Delivered by cesarean section four times more often, 12 percent vs. 3 percent.
  • Underwent epidural injections more than half the time as opposed to 4 percent of deliveries in the 1960s.
  • Received the hormone oxytocin, which is used to speed up labor, 31 percent of the time compared with 12 percent in the 1960s. "Without it, labor might even be longer in current obstetrics than what we found," said lead author Katherine Laughon, M.D., of the epidemiology branch of the Eunice Kennedy Shriver National Institute of Child Health and Human Development.

Data from the more recent deliveries was collected through the NICHD-supported Consortium of Safe Labor.

The analysis was published online in the American Journal of Obstetrics and Gynecology.