Abstract: Objective To investigate the physical development and nutritional status of infants under 6 months of age in Xi'an, and analyze the relevant influencing factors. Methods The convenience sampling method was used to randomly select 10 communities or villages in Xi'an （5 belong to urban sub-district offices and 5 belong to village and town governments）, and randomly select 1 community health service center in each community or village. Infants under 6 months of age who were vaccinated by the immunization program at the selected community health service center from June to August 2021 were selected as the research subjects. The infants were subjected to physical examination （length and weight） and hemoglobin level detection, and infant mothers were subjected to a questionnaire survey. The descriptive analysis method was used to analyze infant malnutrition, and univariate and multivariate analysis methods were used to analyze the influencing factors of infant malnutrition. Results A total of 11 714 infants were included in this study, including 5 951 male infants, accounting for 50.80%, and 5 763 female infants, accounting for 49.20%. Infants under 3 months of age accounted for 45.65%, and 4-6 months of age accounted for 54.35%. A total of 1 972 infants under 6 months of age were malnutrition, and the incidence of malnutrition was 16.83%. The incidence of growth retardation, underweight, wasting, and anemia was 1.15%, 0.96%, 1.47%, and 14.90% respectively. Multivariate Logistic regression analysis showed that the feeding situation （partial breastfeeding OR=1.440, artificial feeding OR=1.523）, the location of household registration （OR=2.396）, the number of complementary food categories added > 2 （OR=1.690）, and the intake of egg yolks （OR=1.657） and fruits （OR=1.355） were the influencing factors of malnutrition in infants under 6 months of age. Conclusion There is a certain risk of malnutrition in infants under 6 months of age in Xi'an, among which anemia is the main malnutrition. Location of household registration, feeding patterns, the number of complementary food categories, and intake of egg yolks and fruits are the influencing factors of malnutrition in infants under 6 months of age, and targeted interventions can be given.

Key words: Physical development, Nutritional status, Infants, Growth and development, Feeding patterns