Antepartum risk factors for moderate to severe neonatal hypoxic ischemic encephalopathy: a Swedish national cohort study.

INTRODUCTION: Our aim was to identify antepartum risk factors for neonatal hypoxic ischemic encephalopathy, with a focus on maternal body mass index and height.

MATERIAL AND METHODS: National population-based cohort study of 692 428 live-born infants ≥36 gestational weeks in Sweden, 2009-2015. Data from the Swedish Medical Birth Register and the Swedish Neonatal Quality Register were linked. Short maternal stature was defined as ≤155 cm, and overweight as body mass index ≥25 kg/m2 . Therapeutic hypothermia served as surrogate marker of moderate to severe hypoxic ischemic encephalopathy. Associations between maternal and infant characteristics and hypoxic ischemic encephalopathy were calculated with logistic regression analyses, and risks were presented as odds ratios with 95% confidence intervals.

RESULTS: Moderate to severe hypoxic ischemic encephalopathy occurred in 0.67/1000 infants. Nulliparity, previous cesarean delivery, short stature, overweight, gestational age, occiput posterior presentation and birthweight were all independently associated with hypoxic ischemic encephalopathy. The risk of hypoxic ischemic encephalopathy increased with decreasing maternal height and increasing body mass index. Compared with non-short women (≥156 cm) with normal weight (body mass index <25 kg/m2 ), those with both short stature and overweight had increased risk of hypoxic ischemic encephalopathy (odds ratio 3.66; 95% confidence intervals 2.41-5.55). Among parous women with both short stature and overweight, the risk was almost sixfold (odds ratio 5.74; 95% confidence intervals 3.41-9.66).

CONCLUSIONS: Antepartum risk factors for moderate to severe hypoxic ischemic encephalopathy included nulliparity, previous cesarean delivery, short stature, overweight, gestational age, occiput posterior presentation and birthweight. The combination of maternal short stature and overweight was associated with a more than threefold risk of subsequent hypoxic ischemic encephalopathy.