To observe the influence of premature rupture of membranes (PROM) on neonatal health. A retrospective cohort study was conducted among 3320 in-patient newborns of Bayi Children's Hospital from October 2006 to March 2008. One hundred term newborns and one hundred preterm newborns with PROM were chosen to be compared with fifty normal term newborns and preterm newborns respectively. The data were analyzed with Minitab 12.0 software. Of the 3320 newborns, 711 (21.4%) were complicated with PROM. The morbidity of PROM was 21.4% (711/3320), among whom 9.69% (196/2022) were term newborns, 39.68% (515/1298) were preterm newborns, the differences between the term and the preterm newborns were statistically significant (P<0.001). Preterm newborns with PROM accounted for 72.43% of all PROM newborns (515/711). However, preterm infants only accounted for 30.01% of the newborns without PROM. Sixty-nine newborns with PROM had neonatal respiratory distress syndrome (RDS), incidence of which was 9.7% (69/711): 10 (5.1%) term newborns and 59 (11.5%) preterm newborns, of whom 3 developed broncho-pulmonary dysplasia Among all patients with PROM, 25% (178/711) newborns had different infectious diseases: 92 (12.9%) had pneumonia and 63 (8.9%) had septicemia, which totally accounted for 87.1% of the patients with infectious diseases, 23 (3.2%) newborns had other infectious diseases including peritonitis, purulent meningitis, urinary system infection, skin infection, perianal infection and conjunctivitis, which accounted for 12.9% of the patients with infectious diseases. Blood culture was performed for 163 newborns with PROM, the positive rate of the culture was 38.7% (63/163). The main pathogenic bacteria detected in blood culture were Gram-positive cocci (45.9%) and Gram-negative rods (54.1%). Gram-positive cocci mainly included Staphylococcus haemolyticus and Staphylococcus epidermidis (16/63). Gram-negative rods included K. pneumoniae (19/63) and Escherichia coli (9/63). Fungi were detected in two preterm infants (3.2%). There was no significant difference in the level of total serum bilirubin between term newborns and preterm newborns with PROM (P>0.05). Total serum bilirubin level of 37.1% of total preterm newborns with PROM exceeded 220 micromol/L, while it was 29.1% in term newborns with PROM (P<0.05). There was a significant decrease of blood platelet count (P<0.01) between the PROM group and the normal group. The myocardial enzymes including lactate dehydrogenases, aspartate aminotransferase, creatine kinase, MB isoenzyme of creatine kinase of PROM group were significantly higher than those of the normal group (P<0.05). Compared with the normal group, the average hospital stay of term newborns with PROM and preterm newborns with PROM were prolonged by 20.0% and 25.1% respectively, the average cost of hospitalization of them were increased 30.5% and 60.0% respectively. PROM is harmful to newborns health in many ways. Studies on PROM should be enhanced.