Effect of insulin sensitivity and secretion defects at mid-pregnancy on early postpartum glucose intolerance in women with gestational diabetes mellitus.

Objective: This study aimed to evaluate how insulin sensitivity and secretion defects during mid-pregnancy influence the development of early postpartum glucose intolerance in women diagnosed with gestational diabetes mellitus (GDM). Methods: A total of 1,256 pregnant women diagnosed with GDM between October 2005 and March 2023 were enrolled. Participants were categorized into four groups: GDM-normal, GDM-secretion defect only, GDM-sensitivity defect only, and GDM-mixed defect. Postpartum glucose intolerance was defined as fasting plasma glucose ≥ 100 mg/dL or 2-h plasma glucose ≥ 140 mg/dL during a 75-g oral glucose tolerance test at 6-12 weeks after delivery. Results: Women presenting with a sensitivity defect at mid-pregnancy showed a significantly higher rate of postpartum glucose intolerance than those without sensitivity defect (64.9% vs. 46.6%, P < 0.001). Conversely, the presence of a secretion defect alone did not result in a significant difference. The highest prevalence of postpartum glucose intolerance was observed in patients with GDM-mixed defect (GDM-normal 45.7%, GDM-secretion defect only 48.5%, GDM-sensitivity defect only 62.8%, GDM-mixed defect 91.3%; P for trend < 0.001). The risk of postpartum glucose intolerance was 1.46 times higher (95% CI 1.07-2.00) for the GDM-sensitivity defect only group and 5.43 times higher (95% CI 1.20-24.56) for the GDM-mixed defect group, compared with the GDM-normal group. Conclusions: Among women with GDM, impaired insulin sensitivity identified at mid-pregnancy is associated with a substantially increased risk of early postpartum glucose intolerance, whereas insulin secretion defects are not significantly related to this risk.