A recent study found a correlation of 0.8 between DNAm age and chronological age in uterine endometrium when all of the samples came from the same menstrual time point (LH+ 7, or 7 days after the surge in luteinizing hormone)15, but our correlation was unchanged if we stratified by menstrual phase (LH+ 8), or by endometriosis status. Here, PLOD1 is linked to endometriosis.