Generally the compounded short-acting oral contraceptives now commonly used are taken according to the menstrual cycle and have a regulating effect and do not usually cause early menstruation. However, irregular bleeding may occur if doses are missed or not taken in sequence. In addition, regular use of the emergency contraceptive pill can lead to menstrual disorders and irregular bleeding from the uterus. None of the above abnormal vaginal bleeding is actually strictly speaking considered early menstruation.
In general, the pill does not cause early menstruation, but not taking the combined short-acting pill in the correct way and taking the emergency contraceptive pill regularly can lead to menstrual disorders.