BackgroundBreastfeeding is crucial to the preterm infants. Breast milk is not only food but also medicine. Few studies focused on the longitudinal association with exclusive breastfeeding duration of preterm infants separated from their mothers after discharge, especially in Shanghai. We aimed to examine the exclusive breastfeeding duration amongst first time mothers of preterm infants after discharge and their determinants.MethodsAnalyses were based on 500 preterm infants separated from their mothers in a territory maternity and infant special hospital in Shanghai from September 2018 to September 2019.The self administered questionnaire, breastfeeding knowledge questionnaire, breastfeeding self-efficacy short form scale, Edinburgh postpartum depression scale and breastfeeding family support scale were used for the investigation, and the breastfeeding rate of premature infants was followed up 1 month, 3 months and 6 months after discharge. The changing trend of breastfeeding knowledge, breastfeeding self-efficacy, postpartum depression and family support were measured by ANOVA in different stages.The Kaplan Meier survival curve and Cox regression model were used to analyze the determinants of exclusive breastfeeding duration of premature infants after discharge. ResultsThrough the Cox regression model, we found that the maternal planned pregnancy (RR=0.68, 95%CI=0.53~0.87), delivering breast milk during hospitalization (RR=0.80, 95%CI=1.41~2.29),NICU feeding mode (RR=1.22, 95%CI=0.13~0.38) during hospitalization and family support (RR=0.56,95%CI=1.00~2.43) were the independent factors influencing the exclusive breastfeeding duration after discharge. ConclusionsThe exclusive breastfeeding duration of premature infants was affected by many factors, so we should focus on three levels of individual, family and society, and give targeted intervention measures to increase exclusive breastfeeding rate and prolong exclusive breastfeeding duration.Trial registration: Not applicable