Observational analyses
The observational analyses were performed using R software. We firstly used T-test to estimate the differences in age, BMI, and HGS between male and female in the study population. Then regression analyses was performed to evaluate the associations between C-section and left HGS (n=160,635) and right HGS (n=160,651), respectively. Age, sex, BMI and 10 population structure principal components (PCs, calculated by UK Biobank) were used as covariates.