Association Between First-Trimester Gestational Weight Gain and the Risks of Gestational Diabetes Mellitus and Macrosomia.

Purpose: To investigate the association between first-trimester gestational weight gain and the risks of gestational diabetes mellitus (GDM) and macrosomia. Patients and Methods: This single-center retrospective cohort study was based on our hospital's obstetric record-establishment database. Between January 2022 and January 2025, 516 women with singleton pregnancies were screened, and 500 eligible women were included in the final analysis. Data on pre-pregnancy weight, first-trimester weight, demographic characteristics, fasting plasma glucose, dietary energy intake, and physical activity were collected. Participants were categorized into low, appropriate, and excessive gestational weight gain groups according to weekly gestational weight gain during the first trimester. Multivariable logistic regression, ROC curve analysis, and sensitivity analyses across pre-pregnancy BMI strata were performed. Results: The incidence of GDM (63.1%) and macrosomia (69.0%) was higher in excessive weight gain group. Excessive gestational weight gain in the first trimester was associated with higher odds of GDM (OR = 2.209, 95% CI: 1.313-3.717) and macrosomia (OR = 2.103, 95% CI: 1.235-3.579). Sensitivity analysis across BMI strata suggested a consistently elevated risk trend in the excessive weight gain group. Conclusion: Excessive gestational weight gain during the first trimester was associated with higher risks of GDM and macrosomia. These findings suggest that first-trimester gestational weight gain may be useful as a potential early risk marker, although the conclusions should be interpreted cautiously and require confirmation in future prospective studies.