(1113) Magnesium sulfate infusion during delivery hospitalization is not independently associated with postpartum hemorrhage

Objective: To determine whether intravenous (IV) magnesium sulfate (Mg) use is associated with postpartum hemorrhage (PPH) and peripartum hysterectomy (hyst).

Study Design: This retrospective cross-sectional study utilizes Epic Systems’ Cosmos research platform, a US-based electronic health record database with de-identified patient-level data. All deliveries from 2017-2023 without International Classification of Diseases (ICD)-10 codes for placenta accreta spectrum were included. The exposure was IV Mg use based on the medication administration record. The outcome of PPH was defined by ICD-10 code plus red blood cell transfusion, procedure code for hemorrhage treatment, or receipt of methergine or carboprost. The outcome of hyst was based on Current Procedural Terminology codes. The associations of IV Mg and the outcomes of (1) PPH and (2) hyst were examined using bivariate and multivariate analyses. In addition, these associations were examined stratified by gestational age at delivery (< 32 vs >32 weeks’ gestation).

Results: PPH was significantly associated with all listed covariates in bivariate tests (Table 1). Patients receiving IV Mg were significantly more likely to have PPH [OR 2.55 (95% CI: 2.48-2.61)], which was slightly attenuated after adjustment [aOR 2.01 (95% CI 1.95-2.08)]. Among patients with PPH, IV Mg was associated with higher odds of hyst in both models [OR 4.22 (95% CI 3.64-4.88); aOR 7.72 (95% CI 6.38-9.30)]. In stratified analyses, after adjustment, patients who delivered >32 weeks and received IV Mg had even higher odds of PPH [aOR 8.40 (95% CI 6.90-10.21)] (Table 2). There was no significant association among those who delivered < 32 weeks after adjusting for potential confounders.

Conclusion: IV Mg use was significantly associated with increased risk of PPH but only among those patients who delivered >32 weeks’ gestation. Since IV Mg is administered primarily for eclampsia risk reduction and not for fetal neuroprotection after this gestational age threshold, our findings suggest that severe preeclampsia may drive the association between Mg and hemorrhage. Further exploration is needed.