ObjectiveTo explore the impact of intrauterine growth discordance on physical growth and development during infancy and early childhood in twins, and to provide an evidence-based basis for early childhood healthcare and clinical intervention. MethodsA retrospective cohort study design was adopted, with data sourced from the Yiwu Maternal and Child Health Information Platform, Zhejiang Province from January 2016 to July 2023. A total of 439 pairs of twins were included in the study. Generalized estimating equations (GEE) were used to analyze the association between twin growth discordance and weight, length, and head circumference within 36 months of age. ResultsAmong the 439 pairs of twins, 51 pairs (11.6%) exhibited intrauterine growth discordance. GEE analyses showed that the percentage difference of intrauterine growth discordance was negatively associated with weight (β=-0.013, P<0.001), length (β=-0.033, P<0.001), and head circumference (β=-0.015, P<0.001) within 36 months of age. Among the discordant pairs, the twin with the lower birth weight had a significantly higher risk of being classified as growth-retarded for weight (OR=6.057, 95%CI: 3.956‒9.274), length (OR=5.233, 95%CI: 3.499‒7.827), and head circumference (OR=3.476, 95%CI: 2.004‒6.031) during early childhood. ConclusionAmong twins with intrauterine growth discordance, the twin born with lower birth weight is a risk factor for growth retardation in weight, length, and head circumference during infancy and early childhood. It is suggested that an early identification mechanism should be established for such high-risk groups, dynamic monitoring should be implemented in clinical diagnosis and treatment as well as child health care services, and comprehensive measures such as personalized nutritional interventions should be taken as early as possible.