Effects of Antenatal Dexamethasone on Postnatal Serum Cortisol Levels in Late Preterm Infants

Objectives: 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.

Methods: 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).

Results: 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 ( = .01). Only 1 infant in the aDex group had a cortisol level <3 percentile of the reference value. Rates of hypoglycemia (absolute difference [95% CI] - 1.0 [-16.0,15.0];  = .90) and mechanical ventilation were similar in both groups (absolute difference [95%CI] - 0.3 [-9.3,8.7];  = .94). No deaths occurred.

Conclusion: 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.