Objective: The objective of this study is to estimate the accuracy of early oral glucose tolerance testing (GTT), to predict impaired glucose tolerance.Study Design:This was a prospective cohort study. Women received an early 75 g 2 h GTT between postpartum days 2-4 and again 6-12 weeks postpartum. The ability of the early GTT to accurately detect impaired glucose tolerance and diabetes was assessed by calculating sensitivity, specificity, positive predictive value (PPV) and negative predictive values (NPVs). The routine 6-12-week postpartum GTT was considered the gold standard.Results:The early GTT was completed by 100% of subjects, whereas only 31 of 58 (53%) women returned to complete the 6-12-week postpartum GTT. The early GTT had modest sensitivity for impaired glucose tolerance (62.5%) and overt diabetes (50%). However, it had excellent specificity (100%), PPV (100%) and NPV (96.7%) for diabetes. The NPV for impaired glucose tolerance with the early GTT was 80%.Conclusion:Rates of 6-12 week postpartum GTT completion among patients with gestational diabetes is poor. Appropriate postpartum management may improve by using the early GTT as a screening test.