Published October 24, 2013
Early-term newborns may look as healthy as full-term babies, but a study published in JAMA Pediatrics by University at Buffalo physicians has found they are at significantly higher risk for adverse outcomes.
The researchers found that babies born 37-38 weeks after a mother’s last menstrual period have a greater need for neonatal intensive care compared to those born after 39-41 weeks.
They also found that birth by elective cesarean section pushed health risks even higher.
In an initial study of admission patterns at Women and Children’s Hospital of Buffalo (WCHOB), the researchers found that early-term infants were more likely to suffer some morbidity within a few hours of birth.
Their greatly expanded study shows similar patterns among nearly 30,000 live births at four Buffalo-area hospitals: WCHOB, Millard Fillmore Suburban, Sisters of Charity and Mercy.
Covering calendar years 2006 through 2008, the study is considered the first population-based, countywide assessment of neonatal morbidity among early-term infants based on individual medical records in the United States.
In this large population, adverse outcomes experienced by early-term babies included the following:
The study also found that cesarean delivery is a strong predictor of neonatal morbidity at early-term gestation.
The data show that, compared to full-term babies, early-term babies delivered by cesarean section face a 12.2 percent higher risk for admission to the NICU and a 7.5 percent higher risk for morbidity.
Early-term babies delivered at 37 weeks gestation vaginally face a 9.7 percent risk of admission to the NICU, while those delivered by cesarean section face a 19 percent risk.
Babies delivered by cesarean section have an increased need for respiratory support because they do not experience the hormonal changes of labor, which clear fetal fluid from the lungs, explains senior author Satyan Lakshminrusimha, MD, associate professor of pediatrics.
“Our results show the need for an increased awareness among health care providers,” says corresponding author Shaon Sengupta, MD, a former medical resident in the UB Department of Pediatrics and WCHOB.
“Even though we consider babies born at 37 or 38 weeks almost term, they are still, to a large extent, physiologically immature,” she says.
A JAMA Pediatrics editorial accompanying the research paper notes that the UB study has “important implications for obstetric and neonatal care and research.”
“The findings reinforce the concept that maturation is a continuum, and any preset gestational age cannot be assumed to provide a clear separation between immaturity and maturity,” writes William Oh of Brown University and Tonse N. K. Raju of the Eunice Kennedy Shriver National Institute of Child Health and Human Development.
The early-term babies in the study appeared to be mature, and they did well on the Apgar scores — an initial assessment of basic health measures, notes Lakshminrusimha, who also is chief of neonatology at WCHOB.
However, these positive signs provide “a false assurance to clinical providers and parents,” he says. “They are nevertheless physiologically immature.”
The study confirms what health care providers have observed.
“We were seeing a significant number of infants born at 37 weeks who looked big and pretty healthy, but who, within a few hours developed low blood sugar, difficulty in breathing or needed antibiotics, necessitating admission to the NICU,” says Lakshminrusimha.
Sengupta, who holds a master’s degree in public health from Johns Hopkins University, launched the study as a UB medical resident under Lakshminrusimha’s mentorship.
She is currently completing a neonatal-perinatal medicine fellowship at Children’s Hospital of Philadelphia.
Additional co-authors on the paper, “Adverse Neonatal Outcomes Associated With Early-Term Birth,” are:
The research was funded by UB’s division of neonatology; UB’s Thomas F. Frawley, MD, Residency Research Fellowship Fund; and an American Academy of Pediatrics Resident Research Grant.