Although not all anovulation is caused by cystic ovarian follicles (Wiltbank et al., 2002; Vanholder et al., 2006), additional risk factors of cystic ovarian follicles have been reported as milk production (Laporte et al., 1994; Heuer et al., 1999), parity (Laporte et al., 1994), and stage of lactation (Vanholder et al., 2006).