The Relationship between Body Composition in Early Pregnancy and Gestational Diabetes Mellitus in a Population of Normal BMI Pregnant Women

Background Gestational diabetes mellitus (GDM) is closely related to the short-term and long-term health outcomes of the mothers and offspring. Pre-pregnancy BMI is strongly associated with GDM, nevertheless, it does not distinguish between body fat content and fat distribution. Only using it to assess obesity is flawed. Normal weight obesity (normal BMI but body fat percentage above 30%) and normal weight with central obesity (normal BMI but visceral fat area above 80 cm2) show different degree of metabolic dysregulation. However, those population are usually overlooked in clinical practice and there is a paucity of research on those population and GDM. Objective To explore the correlation between body composition in early pregnancy and GDM in a population of normal pre-pregnancy BMI, and to investigate the relationship between fat distribution and GDM. Methods We performed a study that included 1 938 singleton pregnant women registered in the obstetric out-patient clinic of Beijing Obstetrics and Gynecology Hospital, Capital Medical University from October 2018 to October 2022. They voluntarily underwent nutritional assessment in early pregnancy and had regular pregnancy check-ups until 24-28 weeks of gestation, who underwent body composition testing in early pregnancy (6-16 weeks) and oral glucose tolerance test (OGTT) at 24-28 weeks. According to the OGTT results, the study population were divided into the GDM group (n=382) and the normal group (n=1 556). We estimated the relationship between body composition and fat distribution with GDM in early pregnancy with binary Logistic regression. Results Body fat mass (BFM), visceral fat area (VFA), percentage body fat (PBF), and fat mass index (FMI) in the GDM group were higher than in the normal group (P<0.05). BFM, VFA, PBF, FMI (OR=1.044, 95%CI=1.012-1.078; OR=1.007, 95%CI=1.002-1.012; OR=1.041, 95%CI=1.012-1.070; OR=1.138, 95%CI=1.043-1.241) (P<0.05) and central obesity (VFA≥80 cm2) (OR=1.396, 95%CI=1.101-1.770, P<0.05) associated with a significant increased risk for GDM with binary Logistic regression analysis. Spearman rank correlation analysis showed that BFM, VFA, PBF, FMI and blood glucose of the OGTT test were positively correlated (P<0.05) . Conclusion Among normal pre-pregnancy BMI women, BFM, VFA, PBF, and FMI in early pregnancy were the risk factors of GDM. Central obesity (VFA≥ 80 cm2) could independently predict the development of GDM. It is necessary to pay attention to fat distribution during pregnancy check-ups and to strengthen the pregnancy management for central obesity women.