Effects of antenatal dexamethasone on postnatal serum cortisol levels in late preterm infants

To explore whether antenatal dexamethasone impacts postnatal serum cortisol levels in stable late preterm (LPT) infants. Secondary outcomes were to identify short-term hospital outcomes related to antenatal dexamethasone exposure.

A prospective cohort study of serial serum cortisol levels in LPT infants within 3 h of birth, and at 1, 3, and 14 postnatal days. Serum cortisol levels were compared between infants exposed to antenatal dexamethasone >3 h and <14 days prior to delivery (aDex) and those who either did not receive dexamethasone or were exposed < 3 h or >14 days prior to delivery (no-aDex).

Thirty-two LPT infants (aDex) were compared with 29 infants (no-aDEX). Group demographic characteristics were similar. Serum cortisol levels were identical between the groups at all 4-time points. Cumulative antenatal dexamethasone exposure ranged from 0 to 12 doses. Post-hoc analysis of the 24-hour serum cortisol levels indicated a significant difference between 1 to 3 cumulative doses versus 4 or more doses (p = .01). Only 1 infant in the aDex group had a cortisol level <3^rd percentile of the reference value. Rates of hypoglycemia (absolute difference [95% CI] - 1.0 [-16.0,15.0]; p = .90) and mechanical ventilation were similar in both groups (absolute difference [95%CI] - 0.3 [-9.3,8.7]; p = .94). No deaths occurred.

Antenatal dexamethasone administered 14 days prior to delivery did not affect serum cortisol levels and short-term hospital outcomes in stable LPT infants. Exposure to low cumulative doses of dexamethasone resulted in transient low serum cortisol levels compared to 4 or more doses only at 24-hours.