Must a wife fast and pray if a brownish discharge, not blood, is expelled from her, knowing that she is one and a half months pregnant?

Scholars have differed regarding a pregnant woman's menstruation. Many of them held that a pregnant woman does not menstruate, and this is the madhhab (definition) of Abu Hanifa and Ahmad, and it was chosen by the scholars of the Permanent Committee. Others held that a pregnant woman may menstruate, and this is the madhhab of Malik and Al-Shafi'i, and it was chosen by Muhammad ibn Ibrahim and Ibn Uthaymeen, on condition that the blood has the characteristics of menstrual blood and appears at its usual time. Accordingly, the aforementioned discharge is not menstruation due to the absence of the characteristics of menstrual blood or its timing, and your wife is pure and should do what pure women do.