By Anne Harding

NEW YORK (Reuters Health) - The Centers for Disease Control and Prevention's newest statistics on US births show that preterm births continue to rise, while C-sections accounted for 31.1 percent of births in 2006-an all-time high.

Since 1990, there has been a 20 percent increase in the percentage of babies born preterm, or before 37 weeks gestation. Most of this rise has been driven by so-called "late-preterm" births, or infants born between 34 and 36 weeks' gestation, Joyce A. Martin and colleagues from the CDC's Division of Vital Statistics note in the January 7 issue of National Vital Statistics Reports.

There were nearly 4.3 million babies born in the US in 2006, the report shows, the largest number in more than four decades. While the Healthy People 2010 set a goal of 7.6 percent of babies born preterm, the actual 2006 number was far higher, with 12.8 percent of babies born before 37 weeks in the womb.

Since 1990, Martin and her team note, there has been a 20 percent increase in the percentage of babies born preterm, mostly driven by a rise in late preterm births.

While these babies have fewer problems than infants born before 34 weeks' gestation, who face a host of challenges ranging from digestive difficulties to learning problems, they are still at greater risk than full-term infants, notes Dr. Joann Petrini, who directs the Perinatal Data Center at the March of Dimes in White Plains, New York.

For example, death rates are three times higher among late-preterm infants than full-term babies, while these babies also face a three-fold increased risk of cerebral palsy. "We need to remember that these are still in fact preterm babies," Petrini noted.

Petrini and her colleagues are concerned that elective C-sections and early inductions may be contributing to the continued increase in late-preterm births-which rose 25 percent between 1990 and 2006.

The American College of Obstetrics & Gynecology recommends against delivering babies before 39 weeks' gestation, unless there is a medical reason to do so. A study out earlier this month in The New England Journal of Medicine showed that babies delivered by elective C-section at 37 or 38 weeks-considered full term-still had higher risks of complications including serious infections and breathing problems, and were also more likely to need intensive care. The researchers also found that more than a third of the elective C-sections were performed before 39 weeks.

These findings and others raise the possibility that elective C-sections and inductions may commonly be performed before 39 weeks' gestation without a medical indication, Perini said, and also demonstrate that such early deliveries are not risk-free.

"It's about weighing the risks and the benefits of early delivery," she added. "Some of the studies are really starting to reveal that some of these could be postponed."

SOURCE: National Vital Statistics Reports, January 7, 2009.

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