Doctors in the early 2000s also administered the hormone oxytocin more frequently (in 31 percent of deliveries, compared with 12 percent in the 1960s), the researchers found. Oxytocin is given to speed up labor, often when contractions seem to have slowed. Its use should be expected to shorten labor times, Dr. Laughon explained.
"Without it, labor might even be longer in current obstetrics than what we found," she said.
Their analysis was published online in the American Journal of Obstetrics and Gynecology.
The study compared data from nearly 40,000 deliveries between 1959 and 1966 with records of almost 100,000 deliveries that took place in 2002 through 2008. Data from the recent deliveries were collected through the NICHD-supported Consortium on Safe Labor.
Dr. Laughon conducted the study with D. Ware Branch, M.D., of Intermountain Healthcare and the University of Utah, in Salt Lake City; Jun Zhang, Ph.D., M.D., with the NICHD at the time of the study and now with the Shanghai Jiaotong University School of Medicine, China; and Julie Beaver, M.S., formerly with the NICHD.
Other differences between the two groups reflect changes in later stage delivery practices. For example, in 1960s-era deliveries the use of episiotomy (surgical incision to enlarge the vaginal opening during delivery), and the use of forceps, surgical instruments used to extract the baby from the birth canal, was notably more common.
In current practice, doctors may intervene when labor fai
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NIH/National Institute of Child Health and Human Development