Fig. 2

Reference range. a Reference interval for the methylation levels of 6690 CpG sites which have significant difference in methylation levels between fertile and infertile groups. Red and blue dots show the low and high limit for the 95% confidence interval respectively. b Distribution of the interquartile range for the methylation values of all CpGs in the 450HM array data for the known-fertile samples. c Density of methylation levels for hypo-methylated (blue) and hyper-methylated (red) loci in the fertile reference range exhibit unimodal distributions