Objective To investigate the factors influencing the catch-up growth of 12-months low birth weight infants in Suyu District of Suqian City during the period of COVID-19 prevention and control.

Methods All 301 low birth weight infants were selected with clustered sampling from the database under authorized use， who made their regular check-ups and follow-ups to 12 months in Suyu District of Suqian City from January 2020 to May 2021. Data were collected on infants’ basic information， their birth situation and their weight upon birth and at 12 months， while maternal situation during pregnancy and the infants’ postnatal feeding and diseases were investigated with a questionnaire. Z scores were calculated. All infants were divided into the catch-up growth group and the uncompleted catch-up growth group according to whether the △Z score was ≥0.67. The influencing factors were analyzed for catch-up growth of the low birth weight infants during the period of COVID-19 prevention and control.

Results There were statistically significant differences in the rate of small for gestational age， preterm birth， intrauterine growth retardation， postnatal nutrition enhancement and feeding mode between the two groups. The results in the multifactor logistics regression analysis showed that intrauterine growth retardation （OR=0.070， 95%CI： 0.015‒0.327） was an obstacle factor for catch-up growth， while postnatal fortified nutrition （OR=6.518， 95%CI 1.215‒34.955） was a promoting factor for catch-up growth.

Conclusion There is catch-up growth in postnatal weight among most of the low birth weight infants. Postnatal fortified nutrition is beneficial to catch-up growth， while intrauterine growth retardation may induce uncompleted catch-up growth.