Pregestational BMI Over 23 kg/m2 May Increase Insulin Utilization in Gestational Diabetes Mellitus Patients

The purpose of this study is to examine the pregestational BMI value that results in insulin use in Japanese patients with gestational diabetes mellitus (GDM) and to assess whether the type of GDM treatment affects postpartum glucose tolerance. This retrospective study included 21 GDM patients treated until parturition at our department from 2013 to 2017. We calculated the pregestational BMI related to insulin treatment and the significant elevation in homeostasis model assessment of insulin resistance (HOMA-IR) by receiver operating characteristics curve (ROC) analysis. We also analyzed whether the insulin treatment caused a difference in postpartum glucose tolerance. Seven of the eight patients who needed insulin treatment had a pregestational BMI over 23 kg/m². The pregestational BMI cutoff value related to insulin treatment was 22.5 kg/m² (sensitivity 100%, specificity 46.2%, area under the curve 0.668, and Confidence Interval=0.429-0.907) in ROC analysis. Insulin utilization was significantly higher in the group with a pregestational BMI of 22.5 or more (p=0.045). HOMA-IR at postpartum was higher in patients whose pregestational BMI was 22.5kg/m² or more. Blood glucose levels, HOMA-IR, homeostasis model assessment of β-cell function (HOMA-β), and the insulinogenic index (IGI) after delivery did not differ between the diet and insulin treatment groups. In conclusion, Japanese women with GDM and a pregestational BMI over 23 kg/m² may increase the risk of requiring insulin treatment during pregnancy. Postpartum glucose tolerance did not differ between patients treated with diet or insulin treatment for GDM.