When compared to full-term infants, a new research places higher risk of respiratory illnesses on babies born between 34 weeks and 37 weeks gestation.
The research was conducted by University of Illinois at Chicago and by researcher Dr. Judith Hibbard and colleagues from the Consortium on Safe Labor.
"Even at 37 weeks, babies were three times more likely to have respiratory distress syndrome compared to babies born at 39- or 40 weeks," said Hibbard, UIC professor of obstetrics and gynecology and lead author of the study.
Data were collected from electronic medical records on 233,844 deliveries at 19 hospitals across the U.S. between 2002 and 2008.
Hibbard said respiratory illnesses such as RDS, transient tachypnea, pneumonia and respiratory failure can lead to other problems such as longer hospitalization, the need for a ventilator or antibiotics, and issues with feeding and failure to gain weight.
Using a statistical model, the researchers examined infant respiratory illnesses at each gestational week, controlling for factors that influence respiratory outcomes including maternal medical conditions, length of labor and mode of delivery, and birth weight.
The study found that late preterm births accounted for 9 percent of all deliveries. Thirty-seven percent of late preterm infants were admitted to the neonatal intensive care unit, compared with 7 percent of term infants.
RDS was the most common respiratory illness, occurring in 11 percent of 34-week deliveries. Only 0.3 percent of 40-week deliveries had RDS.
Transient tachypnea, also called "wet lungs," was the second most common respiratory illness, occurring in 6.4 percent of 34-week deliveries, and decreasing to 0.3 percent at 39 weeks.
"The OB community needs to assess indications for induction of labor," said Hibbard, who hopes that this study will help clinicians to counsel their patients about the importance of not requesting medically unnecessary inductions.
The study is published in the July 28 issue of JAMA.