Objective:To investigate the clinical characteristics and prognosis of neonatal chylothorax.Methods:The clinical data of newborns diagnosed with chylothorax from June 2016 to June 2023 in Neonatal Center of Beijing Children's Hospital were retrospectively analyzed, and divided into congenital group and acquired group according to the pathogenesis of chylothorax. The clinical characteristics, treatment methods and prognosis of the two groups were compared.Results:A total of 23 cases were included, including 17 cases (73.9%) in the congenital group and 6 cases (26.1%) in the acquired group. There was no significant difference in gender, gestational age and birth weight between the two groups ( P>0.05). Compared with the acquired group, the proportion of lymphocytes (97.0% vs. 85.0%), the use of erythromycin (7/17 vs. 1/6) and octreotide (9/17 vs. 1/6) and special formula milk feeding (13/17 vs. 2/6) were higher in the congenital group; the proportion of right hydrothorax (1/17 vs. 3/6), invasive mechanical ventilation (6/17 vs. 6/6) and breastfeeding (0/17 vs. 3/6) were lower in the congenital group ( P<0.05). There were no significant differences in terms of the white blood cell count in pleural fluid and plasma protein content, incidence of bilateral and left pleural fluid, proportion of closed thoracic drainage, maximum daily drainage volume, drainage duration, total drainage volume, albumin utilization rate, length of stay and survival rate between the two groups ( P>0.05). 18 cases of pleural effusion absorption without recurrence after conservative treatment; 5 cases died, of which 4 cases died after their parents abandoned treatment, and 1 case died of neonatal necrotizing enterocolitis after thoracic duct ligation surgery. Conclusions:Congenital chylothorax and acquired chylothorax were similar in severity, course of disease and overall prognosis. The utilization rate of erythromycin and octreotide in congenital chylothorax was higher than that in acquired chylothorax. The neonatal chylothorax is usually with an overall good prognosis.