Consumer Reports drew on public billing records from 22 states from 2009 to 2012 to evaluate hospitals that had at least 100 low-risk deliveries in a two-year period. It found the national average rate for first-time cesareans in low-risk women was about 18 percent - much higher than the 12.6 percent rate in 2000, used as a benchmark.
"Because a hospital's C-section rate can be hard to find, it's likely that most families are unaware of the huge differences in medical practice," Consumer Reports said.
Consumer Reports' data did not include factors that can increase the risk of a C-section, such as obesity, diabetes or high blood pressure.
Still, some geographic areas had "dramatic," inexplicable variations. In Los Angeles, for example, cesarean rates in low-risk women ranged from a high of 55 percent at one hospital, to a low of 15 percent at another center.
The range in the Philadelphia region, including South Jersey, was narrower. At the low end were Jennersville Regional in West Grove (12 percent) and Cooper Health System in Camden (13 percent). At the high end were Pottstown Memorial Medical Center (23 percent) and Lourdes Medical Center of Burlington County in Willingboro (28 percent). Asked about their Consumer Reports rates, several local hospitals cited care of high-risk patients such as those carrying multiple fetuses - even though the Consumer Reports analysis focused on low-risk women.
"Like our peers at other large, urban hospitals, many of our deliveries follow high-risk pregnancies requiring special care and close monitoring, which may result in higher-than-average rates of cesarean deliveries," e-mailed Penn Medicine, which last year had 8,885 births at the Hospital of the University of Pennsylvania (16 percent rate in Consumer Reports) and Pennsylvania Hospital (22 percent).
Why do so many women with no clear need for a surgical delivery wind up having one?
A big reason, as Consumer Reports pointed out, is that doctors think labor is moving too slowly - a catch-all problem they call "failure to progress."
Midwives, doulas, and other natural-birth advocates have long argued (and demonstrated) that most slow-progressing women can deliver vaginally if given time and encouragement.
Recent research has bolstered this argument. The Consortium on Safe Labor, a research network of 19 hospitals, published evidence that labor is generally longer now than 50 years ago, reflecting factors such as maternal obesity and age, and drugs used to induce labor and relieve pain.
In March, two influential physician groups - the American College of Obstetricians and Gynecologists and the Society for Maternal-Fetal Medicine - issued new guidelines that cite this change in labor patterns and urge greater patience with women in labor.
Unless complications develop, prolonged labor - over 20 hours with a first delivery or 14 hours in women with previous deliveries - "should not be an indication for cesarean delivery," the guidelines say.
Some obstetricians and hospitals seem to be getting the message.
"We allow patients more time to labor for vaginal delivery to occur instead of proceeding right into a C-section," said Richard Fischer, head of maternal-fetal Medicine at Cooper.
The same strategy has helped Virtua Health's hospitals in Voorhees and Berlin, N.J. to reduce the rate of first-time cesareans by 7 percent over the last four years, to 27 percent, said assistant vice president Kelly Nierstedt. Virtua has also added amenities to support natural birth, including birthing balls, squatting bars on beds, and wireless fetal monitoring so patients in labor can walk around.
Changing practice is "not easy," Nierstedt said. "It's a culture change."