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Loyola study provides evidence that premature girls thrive more than premature boys

Findings also help predict when preemies will go home from hospital

Loyola University Health System

A new study from Loyola University Medical Center provides further evidence that female infants tend to do better than males when born prematurely.

The study found that female infants independently orally fed one day earlier than males. The ability to suck, swallow and breathe simultaneously are reflexes that many premature infants are unable to do. Learning to master these skills and eat independently without feeding tubes is necessary before an infant can safely go home from the hospital.

Researchers set out to determine the mean age when premature infants are able to eat orally from a bottle or the breast and whether gender, gestational age, delivery route or birth year affects this reflex.

They conducted a retrospective review of 2,700 preterm infants born before 37 weeks of pregnancy who were admitted to a level III neonatal intensive care unit between 1978 - 2013. They found that premature infants achieved independent oral feeding at 36 weeks and four days on average. In addition to their gender findings, researchers revealed that being born before 29 weeks of pregnancy negatively influenced the infants' ability to eat independently (37 weeks and three days versus 36 weeks and one day for babies born between 29 - 33 weeks of pregnancy and 36 weeks and three days for babies born late preterm between 34 - 36 weeks and six days of pregnancy). Preterm infants born with severe complications also experienced a delay in independent oral feeding.

Babies born vaginally transitioned to independent oral feeding three days earlier than babies born via C-section. Preterm infants born before 2000 also achieved independent oral feeding two days later than babies born more recently. These findings were published in the latest issue of the Journal of Neonatal-Perinatal Medicine. Since 1981, the preterm birth rate in the United States has increased by more than 33 percent, and in 2012, 11.5 percent of all births were preterm (<37 weeks of pregnancy), with 29 percent of preterm births occurring before 34 weeks of pregnancy. Many advances in medical care have led to improved survival of extremely preterm infants. However, despite increased survival, those born at less than 28 weeks continue to have a high incidence of medical complications. The average length of stay in the NICU has risen due to the increasing survival of extremely preterm infants.

This study confirms that the majority of preterm newborns can be safely discharged three to four weeks before their due date. A this time, newborns are mature enough to maintain their temperature, consistently gain weight and coordinate sucking, swallowing, eating and breathing without gagging or choking.

"This study gives us insight into the factors that influence when an infant is likely to eat independently without complications," said Jonathan Muraskas, MD, senior author, and co-medical director, neonatal intensive care unit, Loyola University Health System, and professor, Loyola University Chicago Stritch School of Medicine. "This information will allow parents and the healthcare team to better plan for when the infant will go home from the hospital."

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Other study authors included Sarah Van Nostrand, DO, Larry Bennett, MD, medical student Victoria Coraglio and biostatistician Rong Guo from Loyola University Health System.

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