Obstetric emergencies as antecedents to neonatal hypoxic ischemic encephalopathy, does parity matter?

Introduction: Our aim was to investigate the risk of moderate to severe hypoxic ischemic encephalopathy (HIE) by obstetric emergencies, with focus on the distribution of obstetric emergencies by parity, taking the history of a previous cesarean into account. Material and methods: Population-based cohort study of 692 428 live births at >= 36 weeks of gestation in Sweden, 2009-2015. Data were retrieved by linking the Swedish Medical Birth Register with the Swedish Neonatal Quality Register. Therapeutic hypothermia served as surrogate for moderate to severe HIE. Logistic regression analysis was used to estimate associations between HIE and placental abruption, eclampsia, cord prolapse, uterine rupture, and shoulder dystocia, presented as adjusted odds ratios (aORs) with 95% CI. Results: An obstetric emergency occurred in 133/464 (29%) of all HIE cases, more commonly in the parous (overall 37%; 48% with and 31% without a previous cesarean) than in the nulliparous (21%). Among nulliparas, shoulder dystocia was the most common obstetric emergency with the strongest association with HIE (aOR 48.2; 95% CI 28.2-82.6). In parous women without a previous cesarean, shoulder dystocia was most common, but placental abruption had the strongest association with HIE. Among parous women with a previous cesarean, uterine rupture was the most prevalent obstetric emergency with the strongest association with HIE (aOR 45.6; 95% CI 24.5-84.6). Conclusions: Obstetric emergencies are common among cases of moderate to severe HIE. The strong association with shoulder dystocia in nullipara, and with uterine rupture in women with previous cesarean deliveries, implies an opportunity for reducing the incidence of HIE.