Gestational Age-Dependent Effects of Antenatal Magnesium Sulfate on Fetal S100B Levels: An Observational Study Using...

Magnesium sulfate (MgSO₄) is widely used for fetal neuroprotection in preterm births before 32 weeks of gestation, yet it remains unclear whether its effect depends on gestational age. S100 calcium-binding protein B (S100B), a protein secreted by astrocytes, is recognized as a biomarker of neural distress. This study aimed to investigate the relationship between antenatal MgSO₄ administration and umbilical cord serum S100B levels, with a focus on gestational age.

This retrospective study included women who delivered between 22⁺⁰ and 33⁺⁶ weeks of gestation at a tertiary center. Patients with hypertensive disorders of pregnancy, category 1 cesarean sections, multiple pregnancies, major congenital anomalies, or insufficient MgSO₄ administration were excluded. Cord blood samples were analyzed for S100B levels using ELISA. Multiple linear regression and restricted cubic spline modeling were performed to assess the association between MgSO₄ and S100B levels across different gestational ages.

Among 69 eligible patients, MgSO₄ administration was significantly associated with higher cord serum S100B levels who delivered at ≥ 30 weeks of gestation (adjusted estimate 0.39, 95% confidence interval 0.17-0.62), but not in those who delivered at < 30 weeks (-0.12, -0.43 to 0.19) in multiple linear regression adjusted for birth weight and antenatal corticosteroids. This association remained consistent across multiple sensitivity analyses. S100B levels exhibited a gestational age-dependent increase in response to MgSO₄, peaking at approximately 32 weeks in restricted cubic spline modeling.

Antenatal MgSO₄ administration beyond 30 weeks of gestation at delivery is associated with increased fetal S100B levels, suggesting a potential gestational age-specific response.