Is it obligatory to fast and pray during the days preceding menstruation, when secretions and a brownish discharge appear, knowing that menstruation might last for 15 days instead of 8 days due to fibroids?

The duration of menstruation may increase, decrease, advance, or be delayed. The criterion for it is the presence of menstrual blood, as long as it does not exceed fifteen days, according to the majority of scholars. However, Sheikh Al-Islam Ibn Taymiyyah holds that if it covers most of the month, then it is considered abnormal bleeding (istiḥāḍah). Discharges and brownish fluid (kudrah) that precede the regular period are not considered part of menstruation.

Sheikh Ibn Jibreen was asked about brownish fluid (kudrah), yellowish discharge (ṣufrah), or a reddish discharge that precedes menstruation, and he replied: "This is abnormal blood (dam fasād) that does not prevent prayer. She should wash her private parts, bind them, perform ablution (wuḍūʾ) for each prayer, and pray until the time for that prayer expires. Then she should perform ablution for the next prayer likewise, unless she is certain that nothing has come out between the two prayer times, in which case there is no need to repeat cleansing (istinjaa') and ablution."

Sheikh Ibn Uthaymeen was asked about the brownish discharge (kudrah) that appears one or two days before the period, and he said: "The brownish discharge (kudrah) that comes one or two days before menstruation is not considered menstruation, based on the hadith of Umm Atiyyah: '[We used not to consider the yellowish discharge (ṣufrah) and brownish discharge (kudrah) as anything].'"

Sheikh Ibn Uthaymeen also clarified that yellowish discharge (ṣufrah) before menstruation is not considered anything, and yellowish discharge after menstruation is not considered anything. However, yellowish discharge during menstruation is considered something, because she has not yet become pure. So, if the yellowish discharge occurs between two flows of blood, it is part of menstruation. But if yellowish discharge is seen, and then menstruation begins, or if a woman becomes pure and then sees yellowish discharge, this yellowish discharge is not considered anything. Menstruation is only what occurs during the menstrual period itself.