Objective To investigate the predictive value of glycated hemoglobin (HbA1c) levels for the risk of macrosomia in patients with gestational diabetes mellitus (GDM). Methods A retrospective study was conducted on 59 GDM patients with macrosomia and 59 GDM patients without macrosomia who visited The Second People's Hospital of Wuhu from May 2021 to May 2024. The study group consisted of patients with macrosomia, while the control group included those without macrosomia. Oral glucose tolerance tests (OGTT) and HbA1c levels were measured during weeks 24 to 28 of pregnancy, and clinical data of the patients were collected. Multivariate logistic regression analysis was used to assess the impact of HbA1c and other factors on the occurrence of macrosomia. Receiver operating characteristic (ROC) curves were plotted to analyze the predictive value of HbA1c for macrosomia risk. Results The fasting plasma glucose (FPG), 1-hour postprandial glucose (1 h PG), 2-hour postprandial glucose (2 h PG), and HbA1c levels were significantly higher in the study group than in the control group (P<0.05). Multivariate logistic regression analysis showed that pre-pregnancy body mass index (BMI), gestational weight gain, FPG, and HbA1c were independent risk factors for macrosomia in GDM patients (P<0.05). ROC curve analysis indicated that the area under the curve (AUC) for predicting macrosomia in GDM patients using HbA1c was 0.898 (P<0.05). Conclusion HbA1c has certain value in predicting macrosomia risk in GDM patients, which is helpful for improving maternal and neonatal health outcomes