Early pregnancy weight gain in pregnant women and the risk of gestational diabetes: a dose–response meta-analysis

Background Gestational diabetes mellitus is the most common metabolic disorder of pregnancy, and its global prevalence continues to rise. Although excessive gestational weight gain has been linked to an increased risk of gestational diabetes mellitus, the precise dose–response relationship during the early pregnancy remains unclear. This study aimed to systematically evaluate the association between early pregnancy weight gain (defined as first-trimester weight gain, approximately 12–13 weeks) and the risk of developing gestational diabetes mellitus and to quantify the dose–response relationship. Methods A systematic search of PubMed, Embase, Web of Science, the Cochrane Library, China Biology Medicine disk, VIP Database for Chinese Technical Periodicals, WanFang Data, and China National Knowledge Infrastructure was conducted from database inception to December 2025 to identify studies examining the association between first-trimester weight gain and the risk of gestational diabetes mellitus. Two reviewers independently performed literature screening, data extraction, and risk of bias assessment. A traditional meta-analysis was performed using Stata 17.0 with a random-effects model using restricted maximum likelihood (REML) and Knapp–Hartung adjustment. The dose–response relationship was examined using restricted cubic spline regression and generalized least squares estimation. Subgroup analyses by GDM diagnostic criteria were performed. Results Nine cohort studies, encompassing 66,673 participants and 13,130 incident cases of gestational diabetes mellitus, were included in the meta-analysis. In the primary analysis restricted to seven studies with strict first-trimester weight gain, insufficient weight gain was associated with a lower risk of GDM (RR 0.84, 95% CI 0.79–0.90), whereas excessive weight gain was associated with a 32% higher risk (RR 1.32, 95% CI 1.20–1.45). Each 1-kg increment in first-trimester weight gain was associated with a 19% increase in GDM risk (RR 1.19, 95% CI 1.15–1.23). No statistically significant departure from linearity was observed ( P for non-linearity = 0.973). Subgroup analysis by GDM diagnostic criteria showed no significant between-subgroup difference for excessive weight gain ( p = 0.810) and a borderline difference for insufficient weight gain ( p = 0.082). Conclusion Current evidence indicates that excessive first-trimester weight gain is associated with an increased risk of gestational diabetes mellitus, and no statistically significant departure from linearity was observed for the dose–response association between first-trimester weight gain and the risk of gestational diabetes mellitus. Weight monitoring and early intervention during the first trimester should be prioritized in clinical practice to reduce the risk of gestational diabetes mellitus. Systematic review registration https://www.crd.york.ac.uk/PROSPERO/view/CRD420251140857 .