Antenatal corticosteroids-to-delivery interval associates cord blood S100B levels

Aim Antenatal corticosteroids (ACS) are recommended for women at risk of preterm birth before 34 weeks' gestation. However, adverse effects of ACS on the fetal brain have also been reported. The time interval from ACS administration to delivery (ACS-to-delivery interval) might alter the effect of ACS on the fetal brain. This study aimed to evaluate the effect of ACS-to-delivery interval on cord blood S100 calcium-binding protein B (S100B) levels as a biomarker of brain damage.Methods Women who delivered between 2012 and 2020 at a tertiary medical center were divided into three groups according to ACS use and ACS-to-delivery interval, retrospectively: non-ACS, ACS <= 7 days, and ACS > 7 days. Patients who did not complete the ACS regimen were excluded. The primary outcome was cord blood S100B levels.Results Cord blood S100B levels were significantly lower in the ACS <= 7 days group than in the non-ACS and ACS > 7 days groups. In the multiple regression analysis, birth & LE;7 days after ACS showed a significant negative association with S100B level (p < 0.001).Conclusions Reduced S100B levels were observed in infants born <= 7 days after ACS but not in infants born > 7 days after ACS. These findings suggest the importance of ACS timing to optimize its effects on the fetal brain, although further studies are required to identify these mechanisms.