The number of preterm births in the United States grew by more than a third between 1996 and 2004, and Cesarean sections accounted for the vast majority of the increase, researchers said this week.
Most of the upsurge involved what physicians call late-preterm babies, those born after 34 to 36 weeks of gestation rather than the normal full term of 38 to 42 weeks.
Physicians are concerned about the growing number of late-preterm babies -- which now account for 72% of all preemies -- because recent studies have shown serious health risks for them, including immature organs, breathing problems, feeding problems, difficulties regulating body temperature, jaundice and a threefold increase in death during the first year of life.
The number of deaths is small, about three per 1,000 late-preterm births. "But it is a serious problem," said Dr. Alan R. Fleischman, medical director of the March of Dimes Foundation.
Many of the other problems eventually resolve themselves, but the cost of the added care can be substantial.
According to the nonprofit Institute of Medicine, based in Washington, medical costs associated with premature delivery total $26 billion per year in this country. More than 50% of those costs are for complications involving late-preterm babies, Fleischman said.
While many of the C-sections are medically necessary, experts fear that growing numbers are the result of physicians' fears of lawsuits arising from labor complications and mothers' desire to schedule births at convenient times.
Since 1975, the proportion of infants delivered by C-section has increased from 5% to 30%, making C-sections the most common surgical procedures for women.
"To do an elective C-section without a medical indication 20 years ago would have been unheard of," said Bruce Flamm, an obstetrician-gynecologist at UC Irvine who was not involved in the study.
"Ten years ago, it was very controversial. Now it is much less controversial. Many are done today because the mother wants it."
The nonprofit American College of Obstetricians and Gynecologists has guidelines firmly stating that C-sections should not be performed unless there are medical indications for it.
But Dr. Sarah J. Kilpatrick of the University of Illinois at Chicago, chairwoman of ACOG's committee on obstetric practice, noted that some physicians will deliver a baby early for relatively minor reasons, such as a slight increase in the mother's blood pressure.
