Magnesium sulfate and risk of hypoxic ischemic encephalopathy in a high-risk cohort.

BACKGROUND: Hypoxic ischemic encephalopathy contributes to morbidity and mortality among neonates ≥ 360 weeks' gestation. Evidence of preventative antenatal treatment is limited. Magnesium sulfate has neuroprotective properties among preterm fetuses. Hypertensive disorders of pregnancy are a risk factor for hypoxic ischemic encephalopathy and magnesium sulfate is recommended for maternal seizure prophylaxis among patients with pre-eclampsia with severe features.

OBJECTIVES: 1) Determine trends in incidence of hypertensive disorders of pregnancy, antenatal magnesium sulfate and hypoxic ischemic encephalopathy, 2) evaluate the association between hypertensive disorders of pregnancy and hypoxic ischemic encephalopathy and 3) evaluate if, among patients with hypertensive disorders of pregnancy, the odds of hypoxic ischemic encephalopathy is mitigated by receipt of antenatal magnesium sulfate. STUDY DESIGN: We conducted an analysis of a prospective cohort of live births ≥360 weeks' gestation between 2012-2018 within the California Perinatal Quality Care Collaborative registry, linked with the California Department of Health Care Access and Information files. We used Cochran-Armitage tests to assess trends in hypertensive disorders, encephalopathy diagnoses, and magnesium sulfate utilization, and compared demographic factors between patients with or without hypertensive disorders of pregnancy or treatment with magnesium sulfate. Hierarchical logistic regression models were built to explore if hypertensive disorders of pregnancy were associated with any severity and moderate/severe hypoxic ischemic encephalopathy. Separate hierarchical logistic regression models were built among those with hypertensive disorders of pregnancy to evaluate the association of magnesium sulfate with hypoxic ischemic encephalopathy.

RESULTS: Among 44,314 unique infants, the diagnosis of hypoxic ischemic encephalopathy, maternal hypertensive disorders of pregnancy and the use of magnesium sulfate increased over time. Compared to patients with hypertensive disorders of pregnancy alone, patients with hypertensive disorders treated with magnesium sulfate represented a higher risk population. They were more likely to be publicly insured, born 36-38 weeks' gestation, be small for gestational age, have lower Apgar scores, require a higher level of resuscitation at delivery, have prolonged rupture of membranes, preterm labor, fetal distress, and undergo operative delivery (all p-values <0.002). Hypertensive disorders of pregnancy were associated with hypoxic ischemic encephalopathy (aOR 1.26, 95% CI 1.13-1.40, p-value <.001) and specifically moderate/severe hypoxic ischemic encephalopathy (aOR 1.26, 95% CI 1.11-1.42, p-value <.001). Among patients with hypertensive disorders of pregnancy, treatment with magnesium sulfate was associated with 29% reduction in the odds of neonatal hypoxic ischemic encephalopathy (aOR 0.71, 95% CI 0.52-0.97, p-value= 0.03) and a 37% reduction in the odds of moderate/severe neonatal hypoxic ischemic encephalopathy (aOR 0.63, 95% CI 0.42-0.94, p-value=0.03).

CONCLUSION: Hypertensive disorders of pregnancy are associated with hypoxic ischemic encephalopathy and specifically, moderate/severe disease. Among people with hypertensive disorders, receipt of antenatal magnesium sulfate is associated with significant reduction in the odds of hypoxic ischemic encephalopathy and moderate/severe disease in a neonatal cohort admitted to the NICU ≥360 weeks' gestation. The findings of this observational study cannot prove causality and are intended to be hypothesis generating for future clinical trials on MgSO4 in term infants.