GWEIS analyses
GWEIS were conducted by PLINK2.020 for HGS using C-section as an environmental factor. This method considers SNP–environment interaction effects from a regression model, which has been shown that it has more power to detect genetic effects than does a test of association between disease and the genetic variant21. The quality control was assessed for each sample at the SNP levels. SNPs with low call rates (<0.90), low Hardy-Weinberg equilibrium exact test P values (<0.001), or low minor allele frequencies (MAFs <0.01) were excluded. For every single locus, there are two models in the previous gnome-wide association studies, called additive model and dominance model. In this study, to consider the role of C-section, we tested SNPADD×C-section model for each SNP. Significant SNPs were identified atP <5.00 × 10−8.