Background: Transient tachypnea of the newborn (TTNB) is a frequent cause of neonatal respiratory distress. Serum lactate dehydrogenase (LDH), a marker of cellular injury, may help predict disease severity and prognosis.

Objective: To evaluate serum LDH levels as an early predictor of morbidity in neonates with TTNB, defined by duration of NICU stay and incidence of complications.

Methods: A prospective observational study was conducted in the NICU at NIMS University Hospital, Jaipur, between May 2023 and October 2024. Neonates ≥34 weeks gestational age diagnosed with TTNB were included. Serum LDH was measured within 24 hours of admission. The correlation of LDH with NICU stay and complications was analysed using appropriate statistical tests.

Results: Among 140 neonates, 56.43% had elevated LDH (>750 IU/L). Elevated LDH was associated with prolonged NICU stay (8.15 ± 1.28 vs. 3.79 ± 1.32 days; p<0.0001) and higher complication rates (32.91% vs. 4.92%; p<0.0001). Strong correlation existed between LDH and NICU stay duration (r=0.8439), and moderate correlation with complications (r=0.4677).

Conclusion: Elevated serum LDH levels are associated with increased morbidity in neonates with TTNB. LDH may serve as a simple, early biochemical marker for risk stratification and prognostication in these patients. Further large-scale, multicentre studies are recommended to validate these findings