March 30, 2012 at 6:23 PM ETBy Rachael Rettner
For all our advances in medicine, women spend longer in labor now than they did 50 years ago, a new study says.
Women in the study who delivered babies in the mid-2000s took, on average, about 2 hours longer to get through the first stage of labor compared with women who gave birth in the 1950s and 1960s. In the first stage of labor, the cervix opens until it is wide enough to allow the baby's head to pass; the second stage is the actual delivery of the baby.
The findings held even after the researchers took into account differences between the women in the two groups, including their weight, age and ethnicity. Women in the contemporary group tended to be older and weigh more than women in the group that gave birth 50 years ago.
The study suggests that changes in delivery practices, such as more common use of epidurals, may be in part responsible for today's longer labor times, the researchers say.
The study will be published in an upcoming issue of the American Journal of Obstetrics and Gynecology.
Dr. S. Katherine Laughon, of the National Institutes of Health, and colleagues analyzed historic records from 39,491 women who gave birth between 1959 and 1966, and contemporary records of 98,359 women who gave birth between 2002 and 2008. The study included only women who entered labor spontaneously (not those who were induced), and were pregnant with one child.
Fifty-five percent of women in the contemporary group received an epidural, while just 4 percent in the historic group did. The rates for use of oxytocin were 31 percent for women in the contemporary group and 12 percent in the historic group. Epidurals are given to relieve pain; oxytocin can be given to women already in labor to strengthen contractions or speed the progress.
The rate of cesarean section was four times higher in the contemporary group compared to the historic group.
Use of forceps and surgical instruments to extract the baby from the birth canal was more common in the historic group than in the contemporary group.
Women in the contemporary group in their first pregnancy took 2.6 hours longer to complete the first stage of labor compared with women in the historic group also in their first pregnancy. Women in the contemporary group who had had a previous pregnancy took about 2 hours longer to complete the first stage of labor.
The second stage of labor, which ends when the baby is born, was also longer for women in the contemporary group, but the difference was much smaller than the first stage — a few minutes instead of hours.
The researchers don't know exactly why labors are longer today. Epidurals have been found to prolong labor by about 40 to 90 minutes, but they are favored over other methods of pain relief, the researchers say.
More research is needed to find out what other factors increase labor times, the researchers say.
"Women may simply need more time to deliver than they used to," Laughon said.
The finding is important because the definition of "normal" labor time is based on data from the 1950s,Laughon said. This may mean doctors should now wait longer before administering drugs to speed up the labor (including oxytocin) or intervening with a C-section, Laughon said.
Longer labors also increase medical costs. The extra time it took women in the contemporary group to give birth would be expected to increase the cost of each birth by $110, the researchers said.
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