Abstract： Objective:To investigate the short- and long-term outcomes of fetuses with selective fetal growth restriction (sFGR).Methods:A retrospective study was conducted on monochorionic diamniotic (MCDA) twins with sFGR admitted to the Neonatal Intensive Care Unit of Peking University Third Hospital from September 2017 to December 2019. MCDA neonates delivered during the same period without significant complications were selected as the control group. MCDA twins with sFGR were divided into type Ⅰ, Ⅱ, and Ⅲ groups and then further divided into the larger and the smaller fetus subgroups according to the birth weight. These children were followed up by telephone at 2-3 years old. Height-for-age and weight-for-age Z-scores were calculated. Ages and Stages Questionnaire-Third Edition (ASQ-3) was used to determine comprehensive development. Independent sample t-test, one-way analysis of variance, non-parameter test, and Chi-square test (or rank-sum test) were used for statistical analysis. Results:(1) A total of 116 pregnant women with sFGR (232 neonates) were enrolled in this study. There were 43, 40, and 33 mothers and 86, 80, and 66 newborns in type Ⅰ, Ⅱ, and Ⅲ groups, respectively. The control group included 31 pregnant women and 62 neonates. The gestational age at onset of sFGR was younger in the type Ⅱ and Ⅲ groups than in type Ⅰ group [(23.8±4.8) and (24.1±3.1) vs (27.0±6.1) weeks, F=5.19, P<0.05; all P<0.017 during pairwise comparisons]. (2) The incidence of sepsis and treatment abandonment/death in neonates in type Ⅱ and Ⅲ groups were higher than those in type Ⅰ and control groups [neonatal sepsis: 11.3% (9/80) and 6.1% (4/66) vs 2.3% (2/86) and 0.0% (0/62), χ2=6.30, P=0.001; death or treatment abandonment rate:13.8% (11/80) and 10.6% (7/66) vs 3.5% (3/86) and 0.0% (0/62), χ2=4.68, P=0.003; all P<0.017 during pairwise comparisons]. In cases with type Ⅱ or type Ⅲ sFGR, the risk of digestive system diseases was significantly higher in the smaller fetus group than in the larger fetus group [type Ⅱ: 46.2% (37/80) vs 38.7% (31/80), χ2=16.72; type Ⅲ: 47.0% (31/66) vs 34.8% (23/66), χ2=39.69; both P<0.001], while the rate of respiratory system diseases was lower in the smaller fetus group [type Ⅱ: 35.0% (28/80) vs 45.0% (36/80), χ2=36.85; type Ⅲ: 37.9% (25/66) vs 45.4% (30/66), χ2=12.55; both P<0.001]. The incidence of neonatal sepsis in smaller fetuses was higher than that in larger ones in type Ⅱ sFGR [7.5% (6/80) vs 3.7% (3/80), χ2=4.68, P=0.034]. The incidence of neurological complications in larger fetuses was higher than that in smaller ones in type Ⅲ sFGR [15.1% (10/66) vs 4.5% (3/66), χ2=5.72, P<0.001]. (3) In type Ⅱ group, seven neonates died (one case of cerebral hemorrhage, two cases of gastrointestinal perforation, two cases of septic shock, and two cases of necrotizing enterocolitis), and four cases withdrew the treatment. In type Ⅲ group, four neonates died (two cases of necrotizing enterocolitis, one case of gastrointestinal perforation, and one case of cerebral hemorrhage), and three cases withdrew from the treatment. (4) Totally, 71 children in type Ⅰ, 61 in type Ⅱ, and 58 in type Ⅲ group were followed up at the age of 2-3. Children with type Ⅱ or type Ⅲ sFGR lagged behind those in type Ⅰ group and control group in physical growth [ M ( P25- P75), Z-scores:－0.46 (－0.87-0.42),－0.35 (－0.62-0.71), 0.05 (－0.61-0.51), and 0.14 (－0.57-0.75); H=6.20, P=0.001]. In type Ⅱ and Ⅲ groups, the smaller fetuses lagged the larger fetuses in physical growth at 2-3 years of age. ASQ-3 scores in communication, gross motor, fine motor, problem-solving and personal-social areas were all lower in type Ⅱ and Ⅲ groups than in type Ⅰ and control groups. ASQ-3 scores in the five dimensions of the smaller fetuses in the type Ⅱ group were lower than those of the larger fetuses. In the type Ⅲ group, the smaller fetuses had lower ASQ-3 scores in communication and gross motor than the larger ones [communication ability: (42.6±18.8) vs (56.4±9.4) scores, t=19.63, P<0.001; gross motor: (45.5±19.7) vs (54.5±9.7) scores, t=12.64, P=0.003]. Conclusion:The neonatal morbidity is significantly increased in type Ⅱ and Ⅲ sFGR, and babies lagged others in height, weight, and ASQ-3 score at 2-3, which is worthy of early attention.