Dydrogesterone is approved in more than 100 countries including Russia, Ukraine, Kazakhstan and Uzbekistan and widely used for the treatment of progesterone deficiencies such as for management of dysmenorrhea, endometriosis, secondary amenorrhea, irregular cycles, dysfunctional uterine bleeding, pre-menstrual syndrome, threatened and habitual miscarriage, infertility due to luteal insufficiency, as well as part of hormone replacement therapy. There are limited data regarding dydrogesterone's role in achieving cycle regularization from post-marketing settings. There is need to assess the persistence of dydrogesterone therapy in a post-marketing setting after cessation of treatment and whether the persistence, if any, is related to the duration of dydrogesterone therapy. Hence, in this observational program, the goal is to observe the possible implications of such treatment in terms of treatment length and response pattern.