Antenatal Magnesium Sulfate for Tocolysis and Early Enteral Feeding in Preterm Infants: A Retrospective Cohort Study

Antenatal administration of magnesium sulfate (MgSO₄) is employed for fetal neuroprotection, and its extended use for tocolysis remains prevalent in certain regions. The impact of MgSO₄ on neonatal gastrointestinal function is contentious, with evidence indicating variability across subpopulations.

A single-center retrospective cohort study examined preterm infants with a birth weight below 1500 g, admitted to the neonatal intensive care unit at the University of Fukui Hospital, Japan, between April 2015 and October 2023. Among 141 eligible infants, 83 received antenatal MgSO₄ within 1 month before delivery, while 58 did not. Exposure was defined as duration, cumulative dose, and neonatal serum magnesium concentration. The primary outcome was time to achieve full enteral feeding (100 mL/kg/day). Associations were estimated using Cox proportional hazards models with inverse probability weighting to evaluate the effects of gestational and maternal age.

Antenatal MgSO₄ exposure was not significantly associated with time to full enteral feeding (HR, 0.80; 95% CI, 0.59-1.10). Multivariable weighted models suggested heterogeneity of association across gestational and maternal age strata (P for interaction < 0.001). HRs increased with gestational age in each maternal age stratum, suggesting antenatal MgSO₄ exposure was more associated with delayed full enteral feeding at earlier gestational ages, especially among older mothers.

Antenatal MgSO₄ exposure was not significantly associated with delayed enteral feeding, and gestational and maternal ages may explain the conflicting results. These findings suggest that the association between antenatal MgSO₄ and enteral feeding progression varies according to gestational maturity and maternal characteristics.