Abstract: ob＜x＞jective To investigate the relationship between early postnatal fluid load and bronchopulmonary dysplasia (BPD), neonatal necrotizing enterocolitis (NEC), premature brain injury (BIPI), hemodynamic patent ductus arteriosus (hsPDA) and other serious complications in very low and ultra-low birth weight preterm infants.Methods From August 2018 to August 2021, 147 premature infants with birth weight less than 1500g and gestational age less than 32 weeks admitted to NICU Affiliated Hospital of Xuzhou Medical University were selected as the study subjects. According to clinical outcomes, they were divided into experimental group and control group. A retrospective case-control study was conducted to compare the differences of fluid intake and total fluid intake in the first, second, third and fourth days after birth between the experimental group (BPD group, NEC group, BIPI group, hsPDA group) and the control group. The cut-off values of fluid intake and total fluid intake in the first 4 days were determined by ROC curve. Logical regression analysis was performed to analyze the correlation between hsPDA and complications such as BPD, NEC and BIPI.Results The total fluid intake in the experimental group was higher than that in the control group on day 1, 2, 3 and 4 after birth, and the difference was statistically significant (P < 0.05); The cut-off values of NEC group were 98.850ml/kg, 123.455ml/kg, 131.300ml/kg, 147.820ml/kg, 492.055ml/kg on the 1st, 2nd, 3rd, 4th and the first 4 days; In BPD group, the truncation values of fluid intake on days 1, 2, 3, 4 and the first 4 were 95.265ml/kg, 112.110ml/kg, 123.385 ml/kg, 141.360ml/kg, 476.195ml/kg, respectively. In BIPI group, the truncation values of fluid intake on days 1, 2, 3, 4 and the first 4 were 88.550ml/kg, 95.390ml/kg, 119.830ml/kg, 128.555ml/kg, 430.890ml/kg, respectively. HsPDA group with 1, 2, 3, 4 days and 4 days before the order of liquid intake and cutoff value is 98.680 ml/kg, 102.655 ml/kg, 123.965 ml/kg, 140.755 ml/kg, 496.530 ml/kg. The combined hsPDA in BPD, NEC and BIPI groups was analyzed. Logical regression analysis showed that hsPDA was a common risk factor for BPD (P =0.000), NEC (P =0.010) and BIPI (P =0.022). The risk of BPD, NEC and BIPI combined with hsPDA was significantly higher than that of non-BPD, NEC and BIPI groups, the difference was statistically significant (P < 0.05). Conclusion BPD, NEC, BIPI and hsPDA may be associated with high fluid load in early birth, and hsPDA is a high risk factor for BPD, NEC and BIPI. Key words bronchopulmonary dysplasia; Neonatal necrotizing enterocolitis; Premature infant brain injury; Patent ductus arteriosus with significant hemodynamics; Fluid intake; Premature infants; Very low birth weight