"It's about time," said Dr. Mitchell Maiman, chairman of obstetrics and gynecology at Staten Island University Hospital in New York City, who was not involved in the report.
The trend toward C-sections, which increased 60 percent between 1996 and 2009, was worrisome, he said. "It was bad for mothers and babies, and now finally it seems we have been able to halt it or maybe even reverse it a tiny bit," Maiman said.
"But we have a long way to go because the C-section rate is way higher than it should be," he added.
After rising from 21 percent of births in 1996 to about 33 percent in 2009, the 2011 rate held steady at about 31 percent, according to figures released Thursday by the U.S. Centers for Disease Control and Prevention (CDC).
Guidelines from the American College of Obstetricians and Gynecologists (ACOG) and other medical groups have helped to curb elective surgical deliveries, Maiman said. Those guidelines discourage cesarean delivery before 39 weeks without a medical indication.
Staten Island University Hospital has followed such guidelines for more than 15 years, Maiman said. The C-section rate there is about 22 percent, well below the national average.
Some obstetricians welcomed the new findings. "It's great that the overall C-section rate has remained flat," said Dr. Jeffrey Ecker, director of obstetrical clinical research at Massachusetts General Hospital in Boston.
"It has been difficult to demonstrate that the rise of the C-section rate over the past decade has been associated with any meaningful improvement in babies' or mothers' health," said Ecker, who is also chair of ACOG's committee on obstetric practice.
Ecker would prefer to see even fewer cesarean deliveries, but "there is no perfect rate," he said. However, "there are opportunities to move the rate down safely," he added.
The report, based on information from the Natality Data File from the National Vital Statistics System, found that the decline wasn't uniform.
At 38 weeks' gestation, the cesarean delivery rate decreased 5 percent -- a trend seen in 30 states. However, at 39 weeks -- full term -- it rose 4 percent. Thirty-eight weeks is considered early term.
Lead author Michelle Osterman, a health statistician at CDC's National Center for Health Statistics, said it's not possible to pin down the reason for the increase at 39 weeks, which was noted in 23 states. Nor could she predict whether the numbers will continue to hold.
"You never know what's going to happen, and we don't make projections," she said. "But it's significant that [the rate of C-sections] hasn't increased in the past three years."
C-sections became more commonplace for several reasons, Maiman said. Some included convenience for doctors and patients who wanted to schedule a delivery and avoid potential complications of a vaginal delivery. Also, women were uninformed about the benefits of a vaginal delivery, he noted.
For mothers, more than one C-section significantly increases the risk of complications and death, Maiman said. Now, doctors may encourage women who have had a C-section to try a vaginal birth later.
For babies, the danger is the prematurity.
"Any prematurity, even slight prematurity, leads to increased complications for the baby," Maiman said. High rates of asthma and a risk for obesity are also associated with C-section births, he said.
According to the March of Dimes, elective C-sections likely contribute to the number of babies born "late preterm," between 34 and 36 weeks' gestation. Although these babies are usually considered healthy, they are more likely to have medical problems than babies born at full term.
Compared to a full-term baby, an infant born late preterm is more likely to have problems with breathing, feeding and maintaining body temperature, the March of Dimes states.
And a study published earlier this year by University of Michigan researchers found that birth at 39 to 41 weeks provides more developmental advantages compared to birth at 37 to 38 weeks.
"We need to leave mothers alone so that the infant can have a full-term delivery," Maiman said.
For more information on cesarean delivery, visit the March of Dimes.