Study: Timing key in cesarean births

Babies delivered by cesarean section before 39 weeks are more likely to suffer respiratory problems and other complications than later-term births, doctors at UNC-Chapel Hill and other centers report today.

The study, published in the New England Journal of Medicine, examined how well babies fared if they were born surgically before 39 weeks to mothers who had already had one C-section. So-called repeat C-sections are often scheduled before a full-term 40-week gestation to avoid the mother going into labor, which can lead to complications.

According to findings, the timing of birth is important. Scheduling a delivery at 37 weeks of gestation results in a nearly fourfold increased risk of respiratory distress syndrome, in which the baby’s lungs aren’t capable of filling with oxygen, compared with babies born at 39 weeks.

Newborns delivered earlier than 39 weeks also were significantly more likely to have other breathing problems and an infection called sepsis.

"There's a big transition point," said Dr. John Thorp, an obstetrician at UNC Hospitals and one of the study's authors. "Babies have to go from getting oxygen and food via the placenta to using their own lungs and their own gastrointestinal tracts. Our tests aren’t sophisticated enough, and we don’t understand the biology enough, to know what the fetal signals of readiness are."

He said delaying delivery even a few days can make all the difference.

"These findings support recommendations to delay elective delivery until 39 weeks of gestation and should be helpful in counseling," the study's authors concluded.

Today's findings are likely to heighten concerns about the number of C-sections done in the United States. Since the mid-1990s, women have increasingly elected to schedule surgery instead of undergoing a vaginal birth, so that C-sections now account for more than 30 percent of deliveries in the United States. The rate in North Carolina is 31 percent.

Much of the increase stems from women having repeat C-sections for their second and third babies — a choice doctors advocate to avoid a rare but potentially fatal complication when the uterus ruptures at the original incision site. But first-time cesarean deliveries are also climbing, sometimes for the convenience of a doctor’s and patient’s schedules, and other times for medical reasons, such as a stalled labor or a baby positioned feet-first in the womb.