Postnatal Steroid Exposure in Extremely Low Gestational Age Newborns and Kidney Function at 24 Months Corrected Age.

Background: Preterm birth is associated with low nephron endowment, with an increased risk of chronic kidney disease (CKD) later in life. Almost all pregnant women at risk for preterm delivery are given antenatal corticosteroids (ANS) to accelerate lung maturity in preterm neonates. Similar to ANS, postnatal corticosteroids are also given to improve lung function, but the impact on kidney function is unknown. The objective of this study was to determine if duration and timing of postnatal corticosteroids in preterm infants influences kidney function at 24 months corrected age.

Methods: A secondary analysis of the PENUT trial (neonates <28 weeks' gestation) was performed and included surviving participants with serum creatinine measured at 22-26 months corrected gestational age (cGA). Exposure included the presence, type, start date, and duration of postnatal steroids (duration and start date based on postmenstrual age (PMA)). The primary outcome was reduced estimated GFR (GFR <90 ml/min/1.73 m2 at the 24-month CGA timepoint). Outcomes were adjusted for perinatal/neonatal exposures, and neonatal outcomes were compared.

Results: Out of 838 surviving infants, 397 (47%) were exposed to any postnatal steroid. Dexamethasone was the most common exposure (n = 238, median start date at day of life (DOL) 27, median duration of 8 days), followed by hydrocortisone (n = 232, median start DOL 13, median duration 17 days). 348 infants were evaluated at 22-26-month follow-up, 61 of whom had reduced GFR. Hydrocortisone duration of 1-7 days had 2.8 (95% CI = 1.06-7.62) times increased odds of reduced GFR at 24 months corrected age. Although overall steroid exposure was not associated with GFR at follow-up, initiation of dexamethasone at ≤25 weeks PMA was associated with 9.39 (95% CI = 1.61-54.71) increased odds of reduced GFR compared to those given dexamethasone at ≥29 weeks.

Conclusions: Although observational, this study supports an association between postnatal steroid timing, duration, and reduced GFR. Further studies are warranted to better understand this association to protect long-term kidney health.