If pregnancy is ruled out and the ultrasound shows that the endometrium is of moderate thickness, after the progesterone stops, some people will have their period in 2-3 days, some in 7-10 days, or even in half a month, and some may have their period even longer, and this varies from person to person. Because women’s uterine lining thickness is different, or women respond differently to progesterone, an external progestin hormone, the timing of menstruation may not be quite the same. Some women with a moderately thick uterine lining and a sensitive response to progesterone may have their period before they stop taking the pill, some may have their period just after they stop taking the pill, and some may have it for a longer period of time. If a woman has an unplanned pregnancy, oral progesterone cannot promote the onset of menstruation because progesterone itself is a birth control drug. If the uterine lining is thin and scarred, or even if there are adhesions in the cervical canal or uterine cavity, oral progesterone alone may not promote menstruation.