FRIDAY, Feb. 11 (HealthDay News) -- Even if their lungs are mature, babies delivered at 36 to 38 weeks are at significantly increased risk for respiratory and other health problems, new research indicates.

In the study, which did not include babies with major birth defects, researchers compared babies with fetal lung maturity who underwent scheduled delivery at 36 to 38 weeks to those delivered at 39 to 41 weeks.

Infant outcomes examined in the study included: admission to a neonatal intensive care unit (NICU); length of stay in the NICU; overall respiratory problems; respiratory distress syndrome; need for mechanical ventilation; sepsis, hypoglycemia (low blood sugar); and death.

Despite having fully developed lungs, scheduled delivery at 36 to 38 weeks was associated with many more health problems, the investigators found.

The study was scheduled to be presented Friday at the Society for Maternal-Fetal Medicine annual meeting in San Francisco. Research presented at meetings is generally preliminary, experts note, since it has not been subjected to the same rigorous scrutiny as research published in peer-reviewed medical journals.

"Patients need to be counseled carefully if they choose to have a scheduled delivery prior to 39 weeks," study author Dr. Yu Ming Victor Fang, of Hartford Hospital in Connecticut, said in a society news release. "Even if tests indicate that their baby's lungs are mature, delivery prior to 39 weeks is not without risks."

More information

The American Congress of Obstetricians and Gynecologists outlines fetal development.