Objective: To investigate the correlation between maternal glyco-lipid metabolic markers and the triglyceride-glucose index (TyG) during mid-to-late pregnancy and the occurrence of macrosomia in gestational diabetes mellitus (GDM). Methods: Based on a GDM cohort, strict inclusion and exclusion criteria were applied to select mothers who underwent cesarean section at the Nanjing Maternity and Child Health Hospital from January to August 2022. Participants were divided into three groups based on the presence or absence of GDM and neonatal birth weight: normal control group (NC, n = 23), GDM without macrosomia group (GDM-N, n = 23), and GDM with macrosomia group (GDM-M, n = 23). General information and glyco-lipid metabolic markers during mid-to-late pregnancy were collected from the three groups. The TyG index and the homeostatic model assessment of insulin resistance (HOMA-IR) were calculated. Spearman correlation analysis and linear regression models were used to analyze the relationship between maternal indi