Earliest of Early-Term Births at Higher Risk for Mortality

Diedtra Henderson

September 30, 2013

Compared with term infants (39 - 41 weeks), early-term infants born between 37 and 38 weeks' gestational age were at a 7-fold higher risk for neonatal morbidity and had heightened risk for admission to the neonatal intensive care unit (NICU) or neonatology service, according to a retrospective regional study.

Shaon Sengupta, MD, from the Division of Neonatology, Department of Pediatrics, Children's Hospital of Philadelphia, Pennsylvania, and coauthors published the findings of their 3-year population-based cohort study online September 30 in JAMA Pediatrics.

Although neonates born between 37 and 41 weeks' gestational age had been lumped together as a homogeneous, low-risk group, evidence is building that infants born during the earlier part of that 5-week gestational window face myriad heightened risks when compared with infants born later. Dr. Sengupta and colleagues looked at perinatal databases containing details about live births at all major birth hospitals in Erie County, New York, from January 1, 2006, to December 31, 2008.

Some 9031, or 27.0%, of the live births during that period were early term (37 - 38 weeks), which mirrors the national average of 27.6%. Of the early-term births, 38.4% were born by cesarean section, which increased infants' risk for NICU or neonatology service admission by 12.2% and increased mortality risk by 7.5% compared with term births.

"Significantly more early-term neonates (8.8%) required NICU admission or admission to the [neonatology service] compared with term infants (5.3%)," Dr. Sengupta and coauthors write. The adjusted odds ratio (OR) for that comparison was 1.64. Adjustments were made for sex, birth weight, mode of delivery, maternal age, and self-reported maternal race/ethnicity.

"Compared with term infants, early-term neonates [also] had significantly higher risk for the following: hypoglycemia (4.9% vs 2.5%; adjusted OR, 1.92),… need for respiratory support (2.0% vs 1.1%; adjusted OR, 1.93), requirement for intravenous fluids (7.5% vs 4.4%; adjusted OR, 1.68), treatment with intravenous antibiotics (2.6% vs 1.6%; adjusted OR, 1.62), and mechanical ventilation or intubation (0.6% vs 0.1%; adjusted OR, 4.57)." the researchers note. Surfactant use (0.3% vs 0.05%; adjusted OR, 6.29) and respiratory morbidity (5.4% vs 3.3%; adjusted OR, 1.58) were also significantly greater in the early-term neonates compared with term infants.

In an accompanying editorial, William Oh, MD, from the Department of Pediatrics, Women and Infants' Hospital, Providence, Rhode Island, and Tonse N. K. Raju, MD, DCH, from the Eunice Kennedy Shriver National Institute of Child Health and Human Development, Bethesda, Maryland, note the sharply higher risk faced by the earliest of early-term infants. "[T]he rates of morbidity doubled for each gestational week earlier than 38 weeks, such that even at 37 weeks (the first week of the term gestation) the morbidity rates were twice those of 38 weeks," the editorialists write.

Although pointing to a number of limitations in the study, the commentators note that 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."

The study authors echoed that assessment.

"There is a continuous relationship between gestational age and neonatal morbidity from early pregnancy onward, with a nadir at about 39 weeks," the researcher team concludes.

"Targeted obstetric practices and maternal education aimed at reducing early-term deliveries (similar to the Eunice Kennedy Shriver National Institute of Child Health and Human Development effort to reduce late-preterm deliveries) will have a significant influence on health care costs by reducing NICU admissions," they continue. "Further research on maternal factors leading to early-term delivery and its financial effect is required to improve outcomes in the early-term neonatal population."

Support for this study was provided by the Division of Neonatology and Thomas F. Frawley, MD, Residency Research Fellowship Fund, both of the University at Buffalo, New York, and the American Academy of Pediatrics. The study authors and the commentators have disclosed no relevant financial relationships.

JAMA Pediatr. Published online September 30, 2013. Article abstract, Editorial extract

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