TUESDAY, July 27 (HealthDay News) -- Late preterm babies -- those born at 34 to 37 weeks' gestation -- are more likely than full-term babies to suffer respiratory distress syndrome and other respiratory morbidity, though the risk decreases with each additional week of gestation, according to research in the July 28 issue of the Journal of the American Medical Association.

Judith U. Hibbard, M.D., of the University of Illinois in Chicago, and colleagues studied data on 233,844 U.S. births from 2002 to 2008, looking for neonates with respiratory compromise admitted to neonatal intensive care units (NICUs), and comparing late preterm births with full-term births to assess short-term respiratory morbidity in the two groups.

The researchers found that 2,032 of 19,334 babies born late preterm were admitted to NICUs with respiratory morbidity, compared with 1,874 out of 165,993 full-term babies. Respiratory distress syndrome was found in 10.5 and 0.3 percent of babies born at 34 and 38 weeks' gestation, respectively. Incidence of transient tachypnea of the newborn was also higher in babies born at 34 weeks than babies born at 38 weeks (6.4 versus 0.4 percent). The odds for respiratory distress syndrome decreased as gestation approached 38 weeks, at which point the odds were the same as for 39 to 40 weeks. The researchers noted similar patterns for transient tachypnea of the newborn, pneumonia, and respiratory failure.

"We suggest that future studies should focus on indications for late preterm birth. Only by more completely understanding reasons for rising rates of late preterm birth might clinicians be able to initiate salutary interventions to decrease neonatal respiratory morbidity," the authors write.

Abstract
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