This expanded GWAS includes data from 32 cohorts of European ancestry (N=87,802). In most studies age at menarche was determined by self-recall and the mean age at menarche in individual studies ranged from 12.4 to 13.6 years, excluding individuals with menarche <9 and >17 years (Methods, Supplementary Table 1 and Supplementary Note). Genome-wide SNP genotyping was performed using a variety of different platforms (Supplementary Table 2 and Supplementary Note). Therefore, after applying standard quality control measures, we imputed the genotypes for ~2.5 million autosomal SNPs in the HapMap CEU sample using Build 35/36 to allow inverse variance meta-analysis of additive genetic association results from each study. We also meta-analysed results from X chromosome SNPs in studies which had this data available (N=52,781). Test statistics from each cohort were adjusted using genomic control to avoid inflation of results due to population stratification.
