Risk Factors for Neonatal Hypoxic-Ischemic Encephalopathy in the Absence of Sentinel Events

Objective  Hypoxic-ischemic encephalopathy (HIE) may be associated with intrapartum sentinel events or may be unexplained. We sought to identify risk factors for unexplained HIE cases and compare their morbidity and mortality to cases associated with sentinel events. Study Design  Retrospective cohort study of all neonates admitted with suspected HIE treated with whole-body hypothermia from January 2007 through July 2017. Cases of unexplained HIE were compared with those with a sentinel event. Results  A total of 223 neonates met the inclusion criteria, of which 86 (38.6%) experienced a sentinel event and 137 (61.4%) did not. Placental histopathology was performed for 28/31 (90.3%) and 48/53 (90.6%) inborn neonates with and without sentinel events, respectively. Placentas from unexplained HIE cases more often exhibited histologic chorioamnionitis (43.8% vs. 17.9%, p  = 0.02) and funisitis (25% vs. 3.6%, p  = 0.02). Neonatal morbidity and mortality were similar. On multivariable regression, nulliparity (odds ratio [OR], 4.11, 95% confidence interval [CI]: 1.24–13.62) and histologic funisitis (OR, 20.33, 95% CI: 1.11–373.4) remained significant. Conclusion  Other than nulliparity and infection which could be identified on umbilical cord examination following delivery but not on clinical assessment prior to delivery, there are no other identifiable risk factors for HIE in the absence of a sentinel event, and morbidity and mortality are similar between groups.