WHAT'S KNOWN ON THIS SUBJECT: Etiology and timing of onset of neonatal hypoxic-ischemic encephalopathy continue to be controversial. Previous studies suggest antepartum events are the main contributing factors, but have used a broad definition of encephalopathy and included infants with genetic, congenital, and developmental abnormalities.WHAT THIS STUDY ADDS: Our study suggests that when strict criteria defining hypoxic-ischemic encephalopathy are applied with supporting neuroimaging evidence of an acute hypoxicischemic insult, intrapartum events are the final and necessary pathway leading to this condition. abstract OBJECTIVE: To determine whether antepartum factors alone, intrapartum factors alone, or both in combination, are associated with term neonatal hypoxic-ischemic encephalopathy (HIE).
METHODS:A total of 405 infants $35 weeks' gestation with early encephalopathy, born between 1992 and 2007, were compared with 239 neurologically normal infants born between 1996 and 1997. All cases met criteria for perinatal asphyxia, had neuroimaging findings consistent with acute hypoxia-ischemia, and had no evidence for a non-hypoxic-ischemic cause of their encephalopathy.RESULTS: Both antepartum and intrapartum factors were associated with the development of HIE on univariate analysis. Case infants were more often delivered by emergency cesarean delivery (CD; 50% vs 11%, P , .001) and none was delivered by elective CD (vs 10% of controls). On logistic regression analysis only 1 antepartum factor (gestation $41 weeks) and 7 intrapartum factors (prolonged membrane rupture, abnormal cardiotocography, thick meconium, sentinel event, shoulder dystocia, tight nuchal cord, failed vacuum) remained independently associated with HIE (area under the curve 0.88; confidence interval 0.85-0.91; P , .001). Overall, 6.7% of cases and 43.5% of controls had only antepartum factors; 20% of cases and 5.8% of controls had only intrapartum factors; 69.5% of cases and 31% of controls had antepartum and intrapartum factors; and 3.7% of cases and 19.7% of controls had no identifiable risk factors (P , .001).
CONCLUSIONS:Our results do not support the hypothesis that HIE is attributable to antepartum factors alone, but they strongly point to the intrapartum period as the necessary factor in the development of this condition. Pediatrics 2013;132:e952-e959