# Gestational Age‐Dependent Effects of Antenatal Magnesium Sulfate on Fetal S100B Levels: An Observational Study Using Cord Serum

## TL;DR

This study finds that magnesium sulfate given to mothers before 30 weeks of pregnancy does not raise fetal S100B levels, but it does so after 30 weeks, suggesting a gestational age-dependent effect.

## Contribution

The study reveals a gestational age-dependent effect of antenatal magnesium sulfate on fetal S100B levels, a potential biomarker of neural distress.

## Key findings

- MgSO4 was associated with higher S100B levels in fetuses delivered at ≥30 weeks, but not in those delivered before 30 weeks.
- S100B levels showed a gestational age-dependent increase in response to MgSO4, peaking around 32 weeks.
- The association remained consistent across multiple sensitivity analyses.

## Abstract

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.