Hospital-related, maternal, and fetal risk factors for neonatal asphyxia and moderate or severe hypoxic-ischemic encephalopathy: a retrospective cohort study

Abstract

Aim A previous large US study had documented an increased risk of asphyxia in small volume and rural hospitals. Our objective was to evaluate this in all hospitals in Alberta, a Canadian province. Methods Retrospective cohort study of all singleton births ≥ 35-week gestation, in Alberta, from 2002–16 recorded in a perinatal database. Asphyxia was defined as intrapartum stillbirth or neonatal death from asphyxia or Neonatal Intensive Care Unit admission and at least two of the following: a. Apgar score of ≤ 5 at 10 minutes; b. mechanical ventilation or chest compressions for resuscitation within 10 minutes; c. cord pH < 7.00 (venous or arterial), or arterial base excess ≥ 12 at birth. Urban hospitals were defined as those serving a population of ≥ 50 000. Hospital volume was categorized by the following: urban: < 1200, 1200–2399, 2400–3600, > 3600 annual births and Rural: < 50, 50–599, 600–1699 annual births. Data on moderate–severe neonatal hypoxic-ischemic encephalopathy was also obtained from two provincial asphyxia databases for 2010–2016. Results The overall rate of neonatal asphyxia was 2.28 per 1000 births for the study period and was 2.5/1000 in the urban hospitals and 1.35/1000 in the rural hospitals, OR: 1.86 95% CI (1.58, 2.19). The rate of moderate or severe neonatal hypoxic-ischemic encephalopathy was 0.9/1000 and was not associated with urban hospital birth; OR: 1.12 95%CI (0.82, 1.53) hospital volume was also not associated with asphyxia or moderate or severe neonatal hypoxic-ischemic encephalopathy. Conclusions This study observed similar rates of asphyxia and moderate or severe neonatal hypoxic-ischemic encephalopathy for rural and urban hospitals in Alberta and no association with hospital volume.