Women with gestational diabetes mellitus (GDM) are at increased risk of developing type 2 diabetes (T2DM). However, the degree of risk and the timing of progression from normal to a pre-diabetic or diabetic state have not been clearly quantified. In this study we analyzed data from a longitudinal study on a group of women with a history of GDM, that were inserted in an oral glucose tolerance test (OGTT) annual screening program and followed up for 5 years after partum. A three state Markov chain model was proposed to represent the dynamics of changes between metabolic states. We used the data to empirically estimate the one-year transition parameters of the model and make predictions about the possibility that women with normal glucose tolerance or impaired glucose metabolism just after partum will develop overt T2DM in three or five years. Results show that subjects with an impaired glucose metabolism few months after partum will hardly (10%) be in the same state after three years. Women with normal glucose tolerance after partum will have a high probability (0.80) to be in the same state three years after.