The potential reversibility of a reduced incretin effect is unclear. We investigated the incretin effect during third trimester and 3 to 4months postpartum in women with and without gestational diabetes mellitus (GDM). Ten women with GDM (plasma glucose (PG) concentration at 120min after 75g-oral glucose tolerance test (OGTT) (PG120min): 10.1±0.6mmol/l (mean±SEM)) and eight women with normal glucose tolerance (NGT; PG120min: 7.0±0.1mmol/l) were investigated on four occasions: 4h 50g-OGTT and isoglycaemic intravenous glucose infusion during third trimester and 3 to 4months postpartum. In women with GDM, the incretin effect increased significantly postpartum (31±6 vs. 56±6%, p=0.02), whereas the increment in women with NGT was insignificant (35±12 vs. 56±9%, p=0.08). Similarly, the gastrointestinal-mediated glucose disposal (GIGD=100%×(glucoseOGTT-glucoseIIGI)/glucoseOGTT) was reduced to diabetic levels in women with GDM (37±3%), but increased (p=0.030) to normal levels post partum (58±6%). GIGD did not change significantly in NGT women (48±3 vs. 57±6%, p=0.94). Women with GDM exhibit a reduced incretin effect which is fully reversible alongside the restoration of normal glucose homeostasis, whereas the reduction in incretin effect during pregnancy in women with NGT was insignificant. Our results suggest that decreased incretin effect in women with GDM is a fully reversible phenomenon.