LAUSR

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, 21051 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.