Objective To evaluate factors affecting cesarean section (CS) rates in groups 1, 2A, 3, 4A, 5 and 10 of the “Ten Group Classification System” (TGCS). Design Retrospective analysis of deliveries occurred from January 1996 to December 2019. Setting A single hospital in Milan. Population Pregnant women belonging to groups 1, 2A, 3, 4A, 5 and 10 of the TGCS. Methods A binary logistic regression analysis was conducted. Included independent variables were maternal age, neonatal birthweight, immigrant status, use of obstetric analgesia, presence of diabetes, hypertension and obesity. Main outcome measures The effect of independent variables on CS rate was expressed as odds ratio. Results A total of 30591 deliveries were recorded. Advanced maternal age was an independent risk factor (RF) in groups 1, 2A, 3, and 4A; diabetes was a risk factor in groups 1 and 5; obesity was a RF in groups 1 and 2A and a protective one in group 5; hypertension was a RF in groups 2A, 5 and 10; macrosomia was a RF in groups 1, 2A and 3; use of obstetric analgesia was either a RF in group 1, and a protective factor in groups 2A, 5 and 10; immigrant status was either a protective factor in groups 1 and 10, and a RF in group 4A. Conclusion The TGCS is a well-established method to compare CS rates between institutions; however, inside each group, many factors can influence the CS rate and they have to be taken into consideration when comparing CS rates.