The ruling on a woman whose menstrual period returns after it has stopped

Q: A question from: F. M. A. - Riyadh. She says: I am a woman forty-two years old. During my menstrual period, it lasts for four days, then stops for three days, and on the seventh day it returns again in a lighter form, then turns brown until the twelfth day. I used to suffer from a bleeding condition, but it went away after treatment, praise be to Allah. I consulted one of the doctors who are known for their righteousness and piety about my aforementioned condition, and he advised me to purify myself after the fourth day and perform the acts of worship, such as prayer and fasting. I actually continued to follow the doctor's advice for two years. However, some women advised me to wait for a period of eight days. I ask you, Your Eminence, to guide me to the correct course.

A: All the days mentioned, the four and the eight, are all days of menstruation. So you must leave off prayer and fasting during them, and it is not permissible for your husband to have intercourse with you on the days mentioned. You must take a full ritual bath after the four days and pray, and you are permissible for your husband during the period of purity between the four and the eight days. There is no harm in your fasting during that time.
If that occurs in Ramadan, it is obligatory for you to fast during those days. And when you become pure from the eight days, you must take a full ritual bath and pray and fast like other women who are in a state of purity; because the menstrual period—that is, menstruation—increases and decreases, and its days come together and separate.
May Allah guide everyone to what pleases Him, and grant us and you and all Muslims understanding in the religion and steadfastness upon it.