Characteristics and pregnancy outcomes of subtypes of gestational diabetes mellitus based on HOMA-IR and BMI

Aims To identify the characteristics and pregnancy outcomes across different subtypes of gestational diabetes mellitus (GDM) based on insulin resistance and body mass index. Methods This retrospective study included 1804 women who underwent a 75g-OGTT during 22-28weeks of gestation, categorized into normal glucose tolerance (NGT) and GDM. Metabolic indicators were measured, and equation of homeostatic model assessment (HOMA) were used to calculate indices of insulin resistance (HOMA-IR), β-cell secretory (HOMA-B), and insulin sensitivity (HOMA-%S) in early and mid-pregnancy .The cut-off value of HOMA-IR in early pregnancy was determined by ROC curve(1.75), which was combined with pre-pregnancy BMI to group NGT and GDM groups into six subgroups each ,stratified according HOMA-IR ≥ 1.75 or HOMA-IR < 1.75 and BMI < 18.5kg/m2 or 18.5 ≤ BMI < 25kg/m2 or BMI ≥ 25kg/m2. Results Compared with women with NGT (1487), women with GDM(317[17.57%]of the total cohort), were significantly older, had higher BMI, fasting plasma glucose(FPG) ,insulin and lipids in early pregnancy, more pronounced insulin resistance in early and mid-pregnancy, and worse outcomes. Analysis of subgroups provided further information. In early pregnancy, except for the GDM subgroup with HOMA-IR ≥ 1.75/BMI ≥ 25kg/m2 having higher FPG than the control subgroup, other subgroups had similar FPG, fasting insulin, HOMA-IR, HOMA-B, and HOMA-%S compared with the NGT subgroups. At the time of OGTT, the peak of glucose and insulin were out of sync in GDM subgroups, accompanied by increased HOMA-IR and HOMA-B and decreased HOMA-%S except for the GDM subgroup with HOMA-IR < 1.75/BMI < 18.5kg/m2. Compared with the corresponding NGT subgroups, the GDM subgroup had higher rates of neonatal jaundice (36.5% vs 12.5, p < 0.001), LGA (28.8% vs 14.3%, p = 0.004), macrosomia (3.6% vs 3.2%, p = 0.007), NICU (12.2% vs 5.5%, p = 0.046) in women with HOMA-IR > 1.75/18.5kg/m2 ≤ BMI < 25 kg/m2, the rates of LGA and macrosomia were 28.4% and 16% in women with HOMA-IR > 1.75/BMI ≥ 25 kg/m2. While the GDM subgroup had the highest rates of PROM and postpartum hemorrhage in women with HOMA-IR < 1.75/BMI < 18.5kg/m2 and 1-minute Apgar score in women with HOMA-IR < 1.75/18.5kg/m2 ≤ BMI < 25 kg/m2. Conclusion GDM presents a more adverse metabolic profile and severe insulin resistance from early pregnancy, with a greater risk of adverse pregnancy outcomes. Subgrouping based on early BMI and IR in GDM reveals different β-cell function at the time of OGTT, along with varying outcomes.