Combining HbA1c and insulin resistance to assess the risk of gestational diabetes mellitus: A prospective cohort study

Objective: To investigate the association of glycated hemoglobin (HbA1c) and homeostasis model assessment insulin resistance (HOMA-IR) with gestational diabetes mellitus (GDM) risk. Methods: Data for this study were from a prospective cohort in Hangzhou, China. We included pregnant women with HbA1c, fasting insulin, and fasting glucose (FG) measured at 15-20 weeks of gestation and underwent oral glucose tolerance test (OGTT) at 24-28 weeks. Based on HbA1c and HOMA-IR, participants were divided into four groups. We estimated the odds ratios (OR) with 95% confidence intervals (CI) to assess the associations of HbA1c and HOMA-IR with GDM occurrence. Finally, we the potential additive interaction between HbA1c and HOMA-IR by calculating relative excess risk due to interaction (RERI) and the attributable proportion due to interaction (AP). Result: 462 pregnant women were included, of whom 136 (29.44%) developed GDM. Based on HbA1c and HOMA-IR, the study population was divided into four groups, with the percentages of each group being 51.30%, 15.58%, 20.56%, and 12.55%, respectively. The incidence of GDM increased with the increase of HOMA-IR and HbA1c, respectively, and the risk of GDM was significantly increased when both HOMA-IR and HbA1c were elevated. However, no such risk was observed in pregnant women < 35 years. Finally, we found significantly higher FG at 24-28 weeks in the high HOMA-IR and HbA1c group among GDM-positive pregnant women. Conclusions: The incidence of GDM increased with increasing HbA1c and HOMA-IR, and the risk of GDM was significantly increased when both HbA1c and HOMA-IR were elevated. This finding may help to identify highrisk women for GDM early in pregnancy and provide timely interventions.