What is the ruling about the colorful discharge that starts before menstrual period? Can a woman perform worship in this situation?

The colorful discharge of a woman (who menstruates regularly) before menstruation period is considered as menstruation and she is considered to be in menstruation period starting from that time to the end of menstruation. Therefore, she cannot establish prayer or fast on the days of having colorful discharge. However, if the discharge continues after 10 days, the discharge on the following days is not menstruation but istihadah. A woman whose discharge continues more than 10 days performs ablution like excused people do and continues her prayers (Mawsili, al-Ikhtiyar, I, 99).

Although this is the general ruling recorded in the sources of Islamic jurisprudence, if it is known that the discharge seen before menstruation period result from premenstrual hormonal changes and it is identified by a doctor that this is not menstrual bleeding, the colored discharge coming from the women, (whose menstruation periods are fixed) before and after their menstruation are considered as an abnormal bleeding.

Source: Presidency Of Religious Affairs The Turkey, High Board of Religious Affairs FATWAS

How Should A Woman Who Menstruates More Than 10 Days Fulfill Her Acts Of Worship?