Incidence, intrapartum risk factors, and prognosis of neonatal hypoxic–ischemic encephalopathy among infants born 35 weeks gestation or more

Abstract Introduction Neonatal hypoxic–ischemic encephalopathy (HIE) is associated with neonatal mortality, acute neurological injury, and long-term neurodevelopmental disabilities; however, the association between intrapartum factors and HIE remains unclear. Methods This population-based cohort study used linked obstetrical and newborn data derived from the Nova Scotia Atlee Perinatal Database (NSAPD, 1988–2015) and the AC Allen Perinatal Follow-Up Program Database (2006–2015) for all pregnancies with live, non-anomalous newborns ≥35 weeks gestation, not delivered by pre-labour cesarean section. Temporal trends in HIE incidence were described, and logistic regression estimated odds ratios (OR) with 95% confidence intervals (CI) for the association of intrapartum factors with HIE. Results The NSAPD identified 227 HIE cases in the population of 226 711 deliveries from 1988 to 2015. Women with clinical chorioamnionitis in labour (OR 8.0; 95% CI 3.9–16), emergency cesarean delivery (OR 10; 95% CI 7.6–14), shoulder dystocia (OR 3.5; 95% CI 2.1–5.7), placental abruption (OR 18; 95% CI 11–29), and cord prolapse (OR 30; 95% CI 15–61) were more likely to have newborns with HIE. Two-thirds of newborns with HIE had an abnormal intrapartum fetal heart rate tracing. The mortality rate among infants with HIE was 27% by 3 years of age. Neurodevelopmental outcomes in the surviving infants were normal in 43% and showed severe developmental delay in 40%. Conclusion Overall, the rate of HIE was low in infants born at ≥35 weeks gestation. The identification of associated intrapartum factors should promote increased surveillance in these clinical situations and emphasize the importance of careful management to optimize newborn outcomes.