Usefulness of cut-off points of International criteria for prediction of post-partum diabetes and prediabetes among Chinese women with gestational diabetes

Aims: This study tests whether cut-off points of the International Association of Diabetes and Pregnancy Study Group's (IADPSG) criteria had threshold effects on post-partum prediabetes and diabetes among Chinese pregnant women with gestational diabetes mellitus (GDM). Materials and Methods: A total of 507 out of 1000 women with GDM (948 of them enrolled in a lifestyle trial during pregnancy) turned up for the follow-up study and underwent a 75-g 2-h oral glucose tolerance test. GDM was diagnosed based on the IADPSG's criteria while post-partum diabetes and prediabetes were defined by the World Health Organization's. Generalized logit model was used to obtain odds ratios (OR) and 95% confidence interval (CI) of fasting, 1-h and 2-h plasma glucoses (PGs) for post-partum diabetes and prediabetes. Restricted cubic spline was used to identify any threshold effects. Results: At a median of 9.1 weeks post-partum, 3.7% (n = 19) women developed post-partum diabetes and 35.1% (n = 178) developed post-partum prediabetes. Fasting PG ≥ 5.1 mmol/L was associated with markedly increased risk of post-partum diabetes without a discernible threshold (adjusted OR: 3.87, 95% CI: 1.03–14.52) while 2-h PG ≥ 8.5 and ≥ 9.0 mmol/L had threshold effects on post-partum prediabetes (2.10, 1.33–3.30) and diabetes (4.02, 1.04–15.56). The 1-h PG also had a threshold at ≥10.0 mmol/L for prediabetes (1.67, 1.06–2.64), but it was not significant for post-partum diabetes. Conclusions: Among Chinese women with GDM, fasting PG ≥ 5.1 mmol/L was associated with post-partum diabetes without any discernible threshold effects while 2-h PG ≥ 8.5 and ≥ 9.0 mmol/L respectively identified women at high risk of post-partum prediabetes and diabetes.