# S100-alarmins, antenatal corticosteroids and the risk of late-onset sepsis in preterm infants: A prospective cohort study

## TL;DR

This study shows that giving corticosteroids to mothers before preterm birth can reduce infection risk in babies, depending on when the steroids are given.

## Contribution

The study reveals that antenatal corticosteroid timing affects S100A8/A9 levels and late-onset sepsis risk in preterm infants.

## Key findings

- Corticosteroids given 7 days before birth reduced sepsis in C-section births.
- Nocturnal corticosteroid administration was most effective in increasing S100A8/A9 levels.
- Corticosteroids given more than 14 days before birth increased sepsis risk.

## Abstract

Antenatal corticosteroids (aCS) are an important measure improving the outcome of preterm infants. Their influence on late-onset sepsis (LOS) risk remains inconclusive. The alarmin S100A8/A9 protects from LOS by regulating innate immune responses. We examined whether aCS impact on postnatal S100A8/A9 serum-levels and consequently on LOS risk.

In a prospective birth-cohort study of 162 preterm infants born before 32 gestational weeks, we determined postnatal S100A8/A9 serum-levels in relation to the timing of aCS and LOS incidence.

aCS administration within 7 days before birth decreased LOS incidence in infants born via primary C-section compared to infants not exposed to aCS (5/69 (7.2%) vs. 4/27 (14.8%)). This effect was linked to increased S100A8/A9 levels, with nocturnal aCS administration being most effective. Opposite, S100A8/A9 levels were lower and the LOS incidence higher compared to unexposed infants (7/23 (30.4%) vs. 4/27 (14.8%)) when aCS were administered more than 14 days before delivery.

Our data suggest that aCS administration affects the risk of LOS in preterm infants in dependence of the timing of administration by influencing the infant’s S100A8/A9 levels. This underlines the importance of optimal timing of aCS facing imminent preterm birth.