A single Regional Dressage Championship program organized by the United States Dressage Federation (USDF), and recognized by the United States Equestrian Federation, Inc. (USEF), will be held in each of the nine USDF.
If fertilization and/or implantation does not take place, the system is designed to menstruate (the monthly shedding of the uterine lining). In addition, the female reproductive system produces female sex hormones that maintain the reproductive cycle.
These hormones were chosen over the rest of the involved hormones for their paramount roles in the regularity of the cycle. It is necessary to understand the biological proceedings which these equations describe. The duration of the female reproductive cycle is typically 24-35 days.