Is menstruation considered menstruation if it begins with a spot or a drop after a uterine curettage and endometrial cauterization, and the nature of menstruation has changed as a result?

The basic rule is that blood discharged by a woman is menstrual blood. If the blood discharge exceeds fifteen days, it is considered istihadah (non-menstrual vaginal bleeding).

She should perform ghusl (ritual bath) and pray, then follow her previous regular cycle if it was consistent, based on the Prophet's (peace be upon him) saying to Fatimah bint Abi Hubaysh: "No, that is from a vein, but leave prayer for the number of days you used to menstruate, then perform ghusl and pray."

If she does not have a consistent cycle, she should distinguish between menstrual blood and istihadah blood. Menstrual blood is black, has an unpleasant odor, and is thick, unlike istihadah blood.

If there is no distinction, she should observe the predominant duration of menstruation, which is six or seven days, based on what is known about the duration of menstruation among her female relatives, due to the Prophet's (peace be upon him) saying to Hamnah bint Jahsh: "Menstruate for six or seven days, according to Allah's knowledge. Then perform ghusl. When you see that you have become pure and clean, pray for twenty-four nights or twenty-three nights and their days, and fast and pray. That will suffice you. And do so as women menstruate and become pure, according to the appointed times of their menstruation and purity."

A woman with istihadah who has neither a regular cycle nor a distinguishing characteristic falls into categories: one who forgets her time and number (the bewildered), so she observes six or seven days; one who forgets her number but remembers her time; and one who forgets her time but remembers her number.