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A cesarean section may not be risky for a small preemie than a vaginal birth.

Matthew Scherf/iStockphoto.com

A cesarean section may not be risky for a small preemie than a vaginal birth.

When a fetus isn't growing as expected, doctors get worried. Often they decide to deliver a baby like that early by cesarean section, figuring it's the safer way to go.

But C-sections aren't always best for baby, according to new research.

Preemies who were small for their gestational age did better when they were delivered vaginally, researchers found. The babies delivered by C-section were 30 percent more likely to have trouble breathing, a big problem in preemies.

That runs against current thinking that it's best to get these fragile babies out quickly via C-section, then whisk them off to the neonatal intensive care unit. The study's results, though not yet published, are almost certain to become ammunition in ongoing efforts to reduce the number of C-sections performed in the U.S.

 

"We think that the vaginal delivery process must do something to help those kids' lungs mature, whether it's the contractions or the act of transitioning more slowly from inside to outside," says Erika Werner, an assistant professor of obstetrics and gynecology at Johns Hopkins. She's the lead researcher on the study, whose findings she presented Thursday at the annual meeting of the Society for Maternal-Fetal Medicine in Dallas.

The researchers looked at the health of 2,560 babies who were small for their gestational age, and who were delivered between 25 and 34 weeks of pregnancy in New York City hospitals from 1995 to 2003. (Birth before 37 weeks is considered preterm). Forty-six percent were delivered vaginally and 54 percent by C-section.

The C-section babies didn't do any better when it came to common complications of premature birth, such as brain bleeds or seizures. And they had a higher risk of respiratory distress syndrome.

Preemies are much more likely to be delivered by C-section than are full-term babies. In 2009, 46 percent of preemies were born by C-section, compared to 29 percent of full term babies, according to the National Center for Health Statistics.

Being small for gestational age can be caused by a mother's high blood pressure, problems with the placenta and chromosomal problems like Down syndrome. It increases a child's risk of health and developmental problems. Typically about 10 percent of babies are small for gestational age.

Werner is also studying the effect of C-sections on preemies who weren't small for their gestational age, and says she's found no benefit. "Those kids, besides having more respiratory distress, also were more likely to have a low Apgar score," she told Shots. The Apgar test measures a baby's breathing, heart rate, and muscle tone right after birth, and is used to judge how well the baby tolerated birth.

"These findings overturn conventional wisdom that C-sections have few or no risks for the baby," Joe Leigh Simpson, a senior vice president for the March of Dimes, said in a statement yesterday. The organization has led efforts to persuade doctors and mothers to avoid C-sections when possible. "Although in many instances a C-section is medically necessary for the health of the baby or the mother, this research shows that in some cases the surgery may not be beneficial for some infants."