Taking birth control pills soon after menstruation may cause early onset of menstruation, and a few may cause delayed menstruation, because birth control pills, especially emergency contraceptives, contain a large amount of progestin components. When the hormone level retreats the endometrial lining will peel off quickly and there will be withdrawal bleeding, which may be a higher chance of early menstruation. If a woman wants to delay the onset of menstruation when she is about to have her period, it is best to keep giving progestin-based medication, as long as the medication is not stopped, it will not lead to the onset of menstruation, as long as the medication is stopped, menstruation will come soon. Regular use of birth control pills can easily lead to menstrual disorders, and women should always ask their doctor for permission before taking the pills.