Abstract: Objective To explore the effects of birth weight on growth and development among infants aged 1-18 months. Methods A retrospective cohort study was conducted to collect the information on infants born and undergoing physical examination in the Maternal and Child Health Hospital of Huadu District, Guangzhou, from January 2018 to December 2019. The differences and the trends of the changes in weight, length, and ponderal index （PI） among infants with different birth weights from 1 to 18 months were analyzed by One way covariance analysis method and the Mann-Kendall trend test, respectively. The generalized estimation equation models were used to estimate the effect of birth weight on the changes in weight, length, and PI of infants aged 1-18 months. Results A total of 1 937 infants were included in the study, including 1 063 males （54.88%）. The average birth weight was （3.18±0.42） kg, the incidence of small for gestational age （SGA） was 7.95%, and that of large for gestational age （LGA） was 5.01% for all the infants. With the increase of month age, both weight and length increment of SGA, appropriate for gestational age （AGA）, and LGA increased （all P<0.01）, while PI increment decreased （all P<0.01）. After adjusting for related confounders, there were significant differences in body weight increment from 6 to 18 months, body length increment from 1 to 18 months, and PI increment at 1 month among SGA, AGA, and LGA （P <0.05 or P<0.01）. Generalized estimating equation models showed that compared to AGA, the weight increment （β=-0.15）, length increment （β=-0.79）, and PI increment （β=-0.03） of SGA were less, respectively, while the height increment （β=0.78） of LGA was higher. Conclusions The birth weight of infants influences the growth and development of infants aged 1-18 months. Medical staff should do an excellent job in maternal health care during pregnancy and dietary nutrition guidance for postpartum infants, strengthen early growth monitoring and intervention and improve the quality of infant development.

Key words: Birth weight, Infant, Growth and development, Cohort study