Variables
Birthweight was collected by medical records. Fetal macrosomia was defined as birthweight ≥4000 g. Maternal age was defined at the time of preconception examinations. Maternal age was either as continuous or as categorical variable. According to the result of association between maternal age and macrosomia by cubic restricted splines (as shown in Figure 1a), above 30 years old was regarded as “advanced maternal age”. Hyperglycemia was defined as FPG levels > 5.6mmol/L, with no self-reported diabetes mellitus.