Impact of restricting early-term deliveries on adverse neonatal outcomes: a statewide analysis

The "39-Week Rule" was adopted by the American College of Obstetricians and Gynecologists in 2009 to eliminate nonmedically indicated (elective) deliveries before 39 weeks in an effort to improve neonatal outcomes.

Our primary objective was to quantify the effect of this policy change on adverse neonatal outcomes among a cohort of term births in South Carolina.

Deidentified data from all births in the state of South Carolina from 2000 to 2008 (before the 39-week rule) and from 2013 to 2017 (after statewide implementation and enforcement of the rule) were obtained from the South Carolina Revenue and Fiscal Affairs Office. Demographic data and International Statistical Classification of Diseases and Related Health Problems Ninth/Tenth Revision codes were obtained for each birth. Our primary outcome was admission to a neonatal intensive care unit. Our secondary outcomes were respiratory morbidities (including respiratory distress syndrome and transient tachypnea of the newborn), hypoxic-ischemic encephalopathy, seizure, sepsis, birth injuries, hyperbilirubinemia, hypoglycemia, and feeding difficulties. Propensity score analysis was used to control for maternal age, body mass index, race, gestational hypertension, infection, placental abruption, and gestational and pregestational diabetes mellitus. After stratification by propensity score, the Cochran-Mantel-Haenszel test was used to compare groups.

A total of 620,121 infants were liveborn at term during the 2 study periods. After implementation of the 39-week rule, there was a significant reduction in early-term deliveries. In adjusted analyses, neonatal intensive care unit admission was significantly more common in the postimplementation period. Respiratory morbidities were also significantly more common postimplementation. In contrast, there were significant reductions in birth injuries and hyperbilirubinemia in the postimplementation period.

Implementation of the 39-week rule was associated temporally with an increase in adverse neonatal outcomes. The outcomes intended to be reduced by the 39-week rule, including neonatal intensive care unit admission and respiratory morbidity, seem to have increased in incidence despite adherence to the proposed guidelines.