What should a woman do if she experiences intermittent bleeding, followed by a week of clear discharge (al-Qassah al-Bayda’), which is then followed by heavy bleeding resembling menstruation? And is this blood considered menses or istihadah (non-menstrual vaginal bleeding)?

It indicates that the criterion for the duration of menstruation is that if the blood a woman sees, when its duration, along with what comes after it and the intervening periods of purity, does not exceed fifteen days, and the duration of purity seen before that blood was thirteen days or more, then all that she sees is considered menstruation.

However, if the total mentioned duration exceeds fifteen days, or if the duration of purity before seeing the blood does not reach thirteen days, then the woman is considered to be experiencing irregular bleeding (istihada).