What should a woman do if her menstruation is delayed, then she experiences brown discharge, followed by a black thread-like discharge?

Menstrual blood, which prevents a woman from praying, fasting, and engaging in intercourse, is characterized by its black or dark red color, foul odor, and its thick consistency, flowing from the womb in a quantity that is not merely drops or a thread. Brown blood (al-Kudrah), if it appears before the period, is not considered menstruation. As for a black thread, it is not considered menstruation. Scanty spots of blood, like nosebleeds, are not considered menstruation and do not affect the validity of the fast, because they originate from veins.