Interactive effects of prepregnancy overweight and gestational diabetes on macrosomia and large for gestational age: A population-based prospective cohort in Tianjin, China

Aims: Obesity increases risk of gestational diabetes mellitus (GDM) and GDM increases risk of macrosomia but their inter-relations for increased risk of macrosomia remain uncertain. We aimed to examine associations between prepregnancy overweight and macrosomia, and synergistic effects between prepregnancy overweight and GDM on macrosomia. Methods: From 2010 to 2012, 19,622 women in urban Tianjin, China, underwent a 50-g 1-h glucose challenge test (GCT) at 24-28 gestational weeks and followed by a 75-g 2-h oral glucose tolerance test (OGTT) if the GCT value was > 7.8 mmol/L. GDM was defined according to International Association of Diabetes and Pregnancy Study Group's criteria. Overweight was defined as body mass index >= 24.0 kg/m2. Logistic regression was performed to obtain odds ratios (ORs) and 95% confidence intervals (CIs). Additive interaction between prepregnancy overweight and GDM was used to test synergistic effects. Results: In the cohort, 1791 (9.1%) and 1726 (8.8%) of the women delivered a macrosomic infant or a large-for-gestational-age (LGA) infant, respectively. Prepregnancy overweight was associated with increased risk of macrosomia and LGA with adjusted ORs being 2.29 (95% CI: 2.07-2.54) and 2.27 (2.05-2.52), respectively. Copresence of prepregnancy overweight and GDM greatly enhanced the adjusted ORs of overweight alone (ORs for macrosomia and LGA: 2.17, 1.94-2.42 & 2.21,1.98-2.47) and GDM alone (ORs for macrosomia and LGA: 2.01,1.48- 2.72 & 2.14, 1.60-2.87) for macrosomia and LGA to 5.29 (4.07-6.87) for macrosomia and 4.72 (3.66-6.10) for LGA, with significant additive interactions. Conclusions: Prepregnancy overweight increased the risks of macrosomia and LGA independently and synergistically with GDM.(C) 2019 Elsevier B.V. All rights reserved.