Weight Changes and Variability in the First Week of Life: Associations with Mortality in Extremely Preterm Newborns

Background : In extremely preterm newborns (ELGANs, <28 weeks’ gestational age [GA]), early weight trajectories reflect fluid balance, yet thresholds for early risk stratification are lacking. We aimed to evaluate whether percentage weight change (ΔW%) from birth weight (BW) and week-1 weight variability were independently associated with death by postnatal day 7 and to identify clinically relevant thresholds. Methods : We performed a retrospective single-center secondary analysis of the Golden Week Program (University of Alabama at Birmingham NICU, 2014–2021). Newborns <28 weeks’ GA with BW ≥400 g and receiving active treatment were included; exclusion criteria were death ≤48 hours, major congenital anomalies, or incomplete weight data. Multivariable logistic regression was performed, adjusted for GA, 5-minute Apgar score, and BW z-score; optimal cutoffs were derived using the Youden Index. Results : Among 805 neonates, 55 (6.8%) died by day 7. Non-survivors had less negative day-3 ΔW% than survivors (median −5.3% vs −10.7%; p<0.01). Day-3 ΔW% was independently associated with mortality (aOR 1.05; 95% CI 1.02–1.08), with an optimal cutoff of −6.4% (sensitivity 57%, specificity 72%). Among variability metrics, Normalized Total Fluctuation (mean absolute day-to-day change in ΔW%) showed the best discrimination (aOR 1.45; 95% CI 1.29–1.65; AUC 0.84), with an optimal cutoff of 5.3% (sensitivity 76%, specificity 74%). Conclusions : ELGANs who do not lose 5%–7% of BW by postnatal day 3 or exhibit an average day-to-day weight fluctuation >5% of BW are at increased risk of early mortality. These weight-derived metrics may support early risk stratification but require prospective validation.