Abstract: Objective Change of postpartum weight in patients with gestational diabetes mellitus (GDM) is still unclear. This study aimed to explore the differences of 1-year postpartum weight retention between GDM and non-GDM participants and the role of body fat in the process. Methods The research was designed a prospective cohort study. GDM was diagnosed by 75 g oral glucose tolerance test(OGTT); 6-month postpartum fat mass index(FMI) was obtained by dual-energy x-ray absorptiometry(DXA); 1-year postpartum body weight was measured at the follow-up period. Log-binomial regression model was used for multivariate analysis. Results (1) The average weight change of 810 participants at 1 year postpartum was(2. 1 ± 4. 2) kg,the average weight change of GDM and non-GDM women was(0. 9 ± 4. 4) kg and(2. 3 ± 4. 1) kg,respectively. The rate of postpartum weight retention of GDM women was lower than that of non-GDM women(11. 9% vs 26. 4%,P = 0. 000 3).(2) Univariate analysis showed that GDM was negatively correlated with postpartum weight retention(RR = 0. 45,95% CI: 0. 28-0. 72),while high FMI at 6-month postpartum increased the risk of postpartum weight retention(RR = 1. 92,95% CI: 1. 48-2. 49).(3) Multivariate analysis showed that GDM(RR = 0. 47,95% CI: 0. 28-0. 78) and high FMI(RR = 3. 48,95% CI: 2. 60-4. 66) was significantly associated with postpartum weight retention after adjusting for potential confounders.(4)The rate of postpartum weight retention of participants with high FMI was approximately twice that of participants with normal body fat in both GDM women and non-GDM women. Conclusion Postpartum weight retention of GDM patients is well-controlled in Guangzhou,while body fat control and weight management among non-GDM pregnant women should be strengthened urgently.