Objective  To analyze the correlation between early pregnant women’ body mass index (BMI) and gestational complications with macrosomia, so as to provide evidence for early prevention of macrosomia.

Methods  Totally 136 019 full-term singletons and their mothers who received first perinatal care from Jan 1^st 2017 to Dec 31^th 2020 were involved . The data were from Zhongshan Women and Children Hospital’s perinatal management information system. And 4 830 cases of macrosomia and their mothers were recruited as macrosomia group, and propensity scores were given based on their general status. Control group(normal birth weight) was matched in a 1∶2 ratio. Early pregnant women’ BMI and the correlation between gestational complications and macrosomia were analyzed.

Results  Finally 4 828 cases of macrosomia were matched successfully, which meaned 4 828 cases of macrosomia and their mothers were macrosomia group while 9 656 cases of normal birth weight newborns and their mothers were normal birth weight group. The results of multivariate analysis showed that maternal early-pregnancy overweight (OR = 1.68,95% CI: 1.53 − 1.82), obesity (OR = 2.99, 95% CI: 2.60 − 3.44), gestational diabetes mellitus (OR = 1.56, 95% CI: 1.33 − 1.82), polyhydramnios (OR = 1.87, 95% CI: 1.03 − 3.37), and excessive gestational weight gain (OR = 2.21, 95% CI: 1.99 − 2.46) were risk factors of macrosomia. Maternal early-pregnancy underweight (OR = 0.44, 95% CI: 0.38 − 0.51), oligohydramnios (OR = 0.21, 95% CI: 0.06 − 0.73), and insufficient gestational weight gain (OR = 0.56, 95% CI: 0.49 − 0.63) were negatively correlated with macrosomia. No other pregnancy complications were found to be associated with macrosomia.

Conclusion  Maintaining proper bodyweight in early pregnancy, appropriate gestational weight gain, and normal blood glucose level during pregnancy are key measures to prevent the occurrence of macrosomia.