Menstruation
Menstruation is the most visible phase of the menstrual cycle and its beginning is used as the marker between cycles. The first day of menstrual bleeding is the date used for the last menstrual period (LMP). The typical length of time between the first day of one period and the first day of the next is 21 to 45 days in young women, and 21 to 31 days in adults (an average of 28 days).
Estradiol valerate/hydroxyprogesterone caproate
EV/OHPC as a combined injectable contraceptive has a relatively short duration and is associated with a high incidence of menstrual irregularity, for instance polymenorrhea (short and hence fast cycles). This may be unacceptable to many women. Twice-monthly administration of half doses has not been found to improve breakthrough bleeding, though cycle length increased to 20 to 24 days.