Risk factors combine in a complex manner in assessment for macrosomia

Background Macrosomia is a serious public health concern. This study aimed to examine the combined effects of various risk factors on macrosomia. Methods The China Labor and Delivery Survey was a multicenter cross-sectional study that included 96 hospitals. Logistic regression analysis was performed to examine the combined effects of the risk factors for macrosomia. The population attributable risk percentage (PAR%) was calculated for the risk factors. Results A total of 64,735 live births, including 3,739 neonates with macrosomia, were used for the analysis. The weighted prevalence of macrosomia was 5.8%. Pre-pregnancy overweight/obesity, diabetes, and gestational hypertension have a synergistic effect on increasing the rate of macrosomia in mothers aged < 36 years. The highest odds ratio (36.15, 95% CI: 34.38–38.02) was observed in female fetuses whose mothers had both gestational hypertension and diabetes. However, in mothers aged ≥ 36 years, the synergistic effect of gestational hypertension and other factors did not exist, and the risk for macrosomia was reduced by 70% in female fetuses of mothers with both gestational hypertension and overweight/obesity. Pre-pregnancy risk factors (pre-pregnancy overweight/obesity and advanced maternal age) contributed the most to macrosomia (23.36% of the PAR%), and the single largest risk factor was pre-pregnancy overweight/obesity (17.43% of the PAR%). Conclusion Macrosomia was related to several common, modifiable risk factors. Some factors have combined effects on macrosomia (e.g., pre-pregnancy overweight/obesity and diabetes), whereas gestational hypertension varies by maternal age. Strategies based on pre-pregnancy risk factors should be given more attention to reduce the burden of macrosomia.