Acute kidney injury and early mortality in extremely preterm neonates born at 22–27 weeks gestation

Background Extremely low gestational age neonates (ELGANs) remain at high risk for morbidity and mortality. Acute kidney injury (AKI) is increasingly recognized, but data in the most immature neonates, especially those born at 22–23 weeks, are limited. Methods We conducted a retrospective cohort study of inborn neonates at the University of Alabama at Birmingham between 2015 and 2021, born at 22–27 + 6 weeks gestation and ≥ 400 g without major anomalies. Early AKI was defined using KDIGO serum creatinine criteria based on postnatal days 3–7 measurements. The primary outcome was death within 7 postnatal days, and we evaluated AKI with logistic regression models to adjust for gestational age (GA), birth weight z-score, antenatal steroids, 5-min Apgar, and study year. Results Of 813 neonates, 487 (59.9%) had sufficient creatinine data for AKI assessment. Median GA was 25.5 weeks, and birth weight was 717 g. Overall, 60 neonates (12.3%) developed AKI. Incidence decreased with advancing gestation, from 27% in 22-week GA neonates to 5% in 27-week GA neonates. Early mortality occurred in 39 of 487 (8.0%). After adjustment, AKI was associated with higher odds of early mortality (aOR 2.48, 95% CI 0.88–7.02), though this did not reach statistical significance. Severe AKI showed a stronger association (aOR 3.99, 95% CI 0.94–16.9). Conclusions AKI incidence was inversely associated with GA in this large cohort enriched with 22–23-week neonates. Severe AKI may increase early mortality risk, underscoring the need for systematic kidney monitoring in the most immature neonates.