Objective To explore the clinical characteristics of multiple-birth preterm infants with necrotizing enterocolitis (NEC) and examine the effects of multiple births on clinical manifestations and outcomes of NEC infants. Methods In this retrospective study, 234 premature infants with NEC admitted to Shanghai Children's Hospital from July 2014 to June 2021 were included as research objects, among which 79 were multiple premature infants with NEC and 155 were single premature infants with NEC, According to the presence of single/multiple birth, they were divided into two groups of singleton (group A, n = 155) and multiple-birth (group B, n = 79). Twin group of vaginal delivery was divided into primary birth (group C, n = 9 and secondary birth (group D, n = 4) based upon birth order. Twin group was also assigned into two groups of higher birth weight (group E, n = 20) and lower birth weight (group F n = 45. And twin group was divided into two groups of concordant twins (CT, group G, n = 42 and discordant twins (DT, group H, n = 26). The latter group was further divided into DT with higher birth weight (group l, n = 5 and DT with lower birth weight (group J,n= 21). Demographic profiles (birth weight, gestational age & birth mode), clinical data (time of NEC onset, laboratory results & Bell stage), treatment (medical or surgical, intestinal perforation & extent of disease) and outcomes (postoperative complications & in-hospital mortality) were recorded. Results Seventy-nine cases of multiple preterm NEC infants were recruited, including 75 twins and 4 triplets. Seventy-five preterm NEC twins had a mean gestational age of 31. 60 weeks and a mean birth weight of 1 476.51 gram. Bell stage was 1 (n= 35), II (n = 21) and III n = 19 Eighteen cases (24%) underwent operation. As compared with group A, NEC infants in group B had a lower birth weight [1618.77 ± 481.30) g. (1 479.34 ±376.88) g, P = 0.016], higher rates of cesarean delivery [84(54.2%) vs. 65 (82.3%), P < 0.001 ] and assisted reproductive technology [11(7.1%) vs. 21 (26.6%) P < 0.001 ]. However, no differences existed in demographic profiles, clinical manifestations, laboratory results, Bell stage, surgery or outcomes (P > 0.05). There was no significant effect of birth order on demographic profiles, clinical manifestations, laboratory results, Bell stage, surgery or outcomes (P > 0.05) As compared with group E, group F had a lower birth weight [(1677.65 ±458.23) gus. (1382.89±300.81) g,P=0.019], lower WBC count [(12.31 ±4.22) ts. (9.13 plus/minus 4.01) * 109/L P = 0.023], greater intestinal lesion [5(45.4%) ts.0(0.0%), P = 0.002 ] and more postoperative complications [11(100%) 18. 3 (42.9%), P = 0.011 ] No difference existed in demographic profiles, clinical manifestations, other laboratory results, Bell stage, surgery or in-hospital mortality (P > 0.05). As compared with group G, group J had a greater gestational age [(30.95±2.44), (32.71 ±2.30) week, P = 0.027 ] and a higher rate of cesarean delivery [30 (71.4%) ts. 20 (95.2%) P = 0.045) rfloor. However, no differences existed in demographic profiles, clinical manifestations, laboratory results, Bell stage, surgery or outcomes (P > 0.05) Conclusions Multiple-birth NEC infants have no greater severity of Bell stage, more surgery, greater extent of intestinal lesion, more postoperative complications or higher in-hospital mortality. Twins with lower birth weight are prone to greater extent of intestinal lesion and more postoperative complications. However, birth order and discordance of twins have no significant effect on disease severity, surgery or in-hospital mortality. [ABSTRACT FROM AUTHOR]