577: Impact of the '39 week Rule' on adverse neonatal outcomes: a statewide analysis

Abstract

To quantify the rates of adverse neonatal outcomes in term births in pre- and post-statewide implementation of the 39 week rule. De-identified data from all term (> 37 weeks gestational age) births in the state from 2000-2008 (prior to the 39-week rule) and 2013-2017 (after statewide implication and enforcement of the rule) were obtained from the Revenue and Fiscal Affairs Office. Demographic data and ICD9/10 codes were obtained for each birth. Primary outcome was a composite of the incidence of RDS, TTN, HIE, seizure, sepsis, birth trauma (bone fracture or neurologic injury), hyperbilirubinemia, hypoglycemia, feeding difficulties, and NICU admissions. Propensity score analysis was used to control for maternal age, maternal BMI, maternal race, maternal gestational hypertensive disorders, infection, abruption,and diabetes. After stratification by propensity score, the Cochran-Mantel-Haenszel test was used to compare the two groups. 620,121 infants were liveborn at term during the study periods (402,139 pre-, 217,982 post-). There was a significant difference in composite neonatal adverse outcomes between the two study periods. However the direction of the difference varied with propensity score stratification. Stratifications corresponding to lower risk pregnancies experienced an increase in the composite outcome, while stratifications corresponding to higher risk pregnancies experienced a decrease. In adjusted analysis, there were statistically significant reductions in brachial plexus injuries, skeletal injuries, peripheral nervous system injuries, and hyperbilirubinemia between pre and post-implementation periods (p < 0.01 for all comparisons). However, there was a statistically significant increase in respiratory distress syndrome (RDS), transient tachypnea of the newborn (TTN), hypoglycemia, and NICU admissions between pre-and post-implementation periods (p < 0.01 for all comparisons). At a state level, lower risk pregnancies have experienced an increased risk of composite adverse neonatal outcomes following the statewide implementation of the 39 week rule.