Adverse neonatal outcomes associated with early-term birth.

IMPORTANCE Full-term neonates born between 37 and 41 weeks' gestational age have been considered a homogeneous, low-risk group. However, recent evidence from studies based on mode of delivery has pointed toward increased morbidity associated with early-term cesarean section births (37-38 weeks) compared with term neonates (39-41 weeks). OBJECTIVE To compare the short-term morbidity of early-term vs term neonates in a county-based birth cohort using the primary objective of admission to a neonatal intensive care unit (NICU) or neonatology service. DESIGN, SETTING, AND PARTICIPANTS Retrospective population-based 3-year birth cohort study (January 1, 2006-December 31, 2008) at all major birth hospitals in Erie County, New York. All full-term live births comprised the birth cohort; this information was obtained from the hospitals' perinatal databases, and data pertaining to NICU or neonatology service admissions were extracted from individual medical records. EXPOSURE Gestational age of early term (37(0/7)-38(6/7) weeks) vs term (39(0/7)-41(0/7) weeks). MAIN OUTCOMES AND MEASURES Admission to the NICU or neonatology service. RESULTS There were 33,488 live births during the 3-year period, of which 29,741 had a gestational age between 37 and 41 weeks. Of all live births, 9031 (27.0%) were early term. Compared with term infants, early-term neonates had significantly higher risks for the following: hypoglycemia (4.9% vs 2.5%; adjusted odds ratio [OR], 1.92), NICU or neonatology service admission (8.8% vs 5.3%; adjusted OR, 1.64), 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). Delivery by cesarean section was common among early-term births (38.4%) and increased the risk for NICU or neonatology service admission (12.2%) and morbidity (7.5%) compared with term births. Among vaginal deliveries, early-term neonates (6.8%) had a significantly higher rate of NICU or neonatology service admission compared with term neonates (4.4%). CONCLUSIONS AND RELEVANCE Early-term births are associated with high neonatal morbidity and with NICU or neonatology service admission. Evaluation of local prevalence data will assist in implementation of specific preventive measures and plans, as well as prioritize limited health care resources.