Gestational diabetes is one of the three principal types of diabetes mellitus (type 1, type 2, gestational diabetes). It is due to the pancreatic \(\beta \) -cells’ dysfunction or the delayed response of the \(\beta \) -cells to the glycaemic levels, and the marked insulin resistance following a potential hormonal release. It is diagnosed for the first time during pregnancy and may occur anytime during pregnancy. In our study, we are interested in predisposed women to gestational diabetes mellitus (GDM) who are considered as vulnerable subjects to diabetes. For this purpose, we propose a compartmental mathematical model, describing the passage of adult women from the stage pre-diabetes to gestational diabetes and diabetes. The local stability of the model’s equilibrium point is carried out using the Routh–Hurwitz stability criterion while sensitivity analysis is based on the normal forward sensitivity index. A numerical simulation is carried out using different values of parameters. Our discussion indicates how decision-makers should pragmatically act to reduce both gestational diabetes and type 2 diabetes.