Perinatal outcomes associated with magnesium sulfate for preeclampsia without severe features.

OBJECTIVE: To evaluate neonatal outcomes in patients with preeclampsia without severe features who received magnesium for seizure prophylaxis. METHODS: Retrospective cohort study of patients with preeclampsia without severe features delivering ≥32 weeks' gestation at our institution (November 2021-May 2023). The primary outcome was a composite of adverse neonatal outcomes (neonatal intensive care unit [NICU] admission, umbilical artery pH < 7.1, umbilical artery base deficit ≥12, 5-min Apgar <3, neonatal death, culture proven sepsis, and mechanical ventilation). Secondary outcomes included the individual components of the neonatal composite and a maternal bleeding composite. Patients were categorized into those who received intrapartum magnesium and those who did not. Baseline characteristics and outcomes were compared between groups. Multivariable logistic regression estimated the association between magnesium and outcomes, adjusting for characteristics that differed between groups. RESULTS: Of 5327 individuals included in our analysis, 583 met study criteria-439 (75%) received magnesium and 144 (25%) did not. Patients who received magnesium were more likely to have public insurance, medical comorbidities, antenatal aspirin use, earlier gestational age (GA) at delivery, and chorioamnionitis. The odds of composite adverse neonatal outcome were higher in patients who received magnesium (53% vs. 29%; adjusted odds ratio [aOR], 1.85; 95% confidence interval [CI], 1.13-3.04) than those who did not. This was primarily driven by increased odds of NICU admission (aOR, 2.46; 95% CI, 1.46-4.14). When excluding NICU admission from the neonatal composite, there was a significant reduction in the neonatal adverse composite among the magnesium cohort (aOR, 0.43; 95% CI, 0.21-0.88). In addition, the odds of neonatal acidemia were also lower in those who received magnesium (aOR, 0.36; 95% CI, 0.15-0.88). CONCLUSION: While we found an increase in overall adverse neonatal outcomes in patients receiving magnesium for seizure prophylaxis for preeclampsia without severe features, we also noted discordant findings of decreased neonatal acidemia and neonatal morbidity when excluding NICU admission. As there is no consensus for intrapartum magnesium administration for patients with preeclampsia without severe features, these results suggest further study of risks and benefits of intrapartum magnesium sulfate is warranted.