Trimester-specific gestational weight gain and adverse outcomes in GDM women: a retrospective cohort study

Aims: Gestational diabetes mellitus (GDM) is one of the most common metabolic disorders during pregnancy and is associated with an increased risk of multiple adverse pregnancy outcomes (APOs). Gestational weight gain (GWG) is an important indicator for disease monitoring and intervention; however, evidence regarding the associations between trimester-specific GWG patterns stratified by pre-pregnancy body mass index (BMI) and APOs among Chinese women with GDM remains limited. Materials and methods: Retrospective cohort study of 8, 562 singleton GDM pregnancies delivered at Maternal and Child Health Hospital of Guangxi Zhuang Autonomous Region (Feb 2021-Sep 2025). Women were classified into underweight, normal-weight, overweight, and obesity groups by pre-pregnancy BMI. GWG in early pregnancy, before Oral Glucose Tolerance Test (OGTT), and after OGTT was categorized as inadequate, adequate, or excessive per National Health Commission guidelines for GDM. Multivariable logistic regression with Benjamini-Hochberg false discovery rate (FDR) correction and generalized additive models (GAM) were used to assess associations and nonlinear relationships with APOs. Results: The associations between GWG and APOs differed significantly across pre-pregnancy BMI categories. Specifically, excessive GWG before OGTT diagnosis was associated with an increased risk of LGA among normal-weight and overweight women (aOR 1.71, 95% CI 1.38-2.13; and aOR 1.72, 95% CI 1.26-2.37, respectively). Excessive GWG after OGTT diagnosis was associated with an increased risk of preeclampsia (aOR 4.06, 95% CI 2.69-6.12; and aOR 2.49, 95% CI 1.46-4.24, respectively). In addition, excessive GWG before OGTT diagnosis was associated with a lower risk of SGA (aOR 0.39, 95% CI 0.25-0.62) in women with underweight. In women with obesity, no significant associations were observed between GWG and APOs, although the directional trends were generally consistent with those in the overweight group. GAM analyses further supported nonlinear associations between GWG and several APOs. Conclusion: Stage-specific GWG patterns in GDM pregnancies showed heterogeneous associations with APOs across pre-pregnancy BMI categories. These findings suggest that weight management strategies tailored to both pre-pregnancy BMI and gestational stage may help optimize pregnancy outcomes in women with GDM.