Since cdk1 and Mapk are two key genes in oocyte maturation (22), in addition to the fact that Dnmt1 and Hdac1 are two essential genes for normal epigenetic modification and development (11), the difference in the maturation fertilization and embryonic development outcome may be partly induced by the expression alterations of genes in the oocytes of the PCOS and control groups. Here, DNMT1 is linked to polycystic ovary syndrome.