Evaluation of Postpartum Glucose Tolerance Test Results Based on Criteria and Timing

To evaluate postpartum type 2 diabetes testing and classification using the revised 2022 American Diabetes Association (ADA) diagnostic criteria, in comparison with the American College of Obstetricians & Gynecologists' (ACOG) criteria, in women with gestational diabetes mellitus (GDM) across inpatient and outpatient testing settings. Secondarily, we aimed to evaluate whether the timing of administration of the screening test was associated with differences in results.

This was a retrospective cohort study of patients with GDM who delivered at a single institution between 2023 and 2025. The traditional cohort (January-December 2023) was recommended an outpatient 75-g, 2-hour oral glucose tolerance test (OGTT). The hybrid cohort (June 2024-June 2025) was given the option of inpatient screening during the delivery hospitalization or outpatient testing. The primary outcome was OGTT completion. Secondary outcomes were diagnoses of glucose intolerance or diabetes. In January 2022, the ADA revised postpartum diagnostic criteria so that a diabetes diagnosis would require two abnormal values instead of a single abnormal OGTT value. The ACOG and 2022 ADA criteria were applied to OGTT results retrospectively to estimate their effect on postpartum diabetes classification. In a subgroup analysis, we examined whether the timing of postpartum OGTTs influenced the results.

In the traditional cohort, 6,689 deliveries occurred; of these, 309 patients (4.6%) had GDM and met inclusion criteria. In the hybrid cohort, 6,312 deliveries occurred; of these, 276 (4.4%) patients met inclusion criteria. Rates of OGTT completion were higher in the hybrid cohort than in the traditional cohort (73.9% vs 31.7%, P <.001). Inpatient testing yielded higher rates of glucose intolerance (48.0%) and diabetes (15.4%) than outpatient testing in either cohort (traditional: 19.4% glucose intolerance and 4.1% diabetes; hybrid: 20.7% glucose intolerance and 3.4% diabetes). Application of the 2022 ADA criteria resulted in the reclassification of most ACOG-defined diabetes results as glucose intolerant (Bowker χ 2 =24, P <.001). In an adjusted multinomial regression that used ACOG criteria, inpatient testing was associated with glucose intolerance (adjusted odds ratio [aOR] 3.06; 95% CI, 1.57-5.97) and overt diabetes (aOR 4.65; 95% CI, 1.14-18.9) when compared with outpatient testing. Testing on postpartum day 1 relative to outpatient testing was associated with glucose intolerance (aOR 2.20; 95% CI, 1.36-3.57) and overt diabetes (aOR 3.92; 95% CI, 1.69-9.06), whereas testing on or after postpartum day 2 did not show a statistically significant association.

Inpatient screening improves the rate of postpartum testing, but diagnostic classification varies widely by the criteria used (ACOG vs ADA) and test timing (postpartum day 1 vs 2), which underscores the need for national guidance on optimal timing and interpretation of postpartum OGTTs.