What is the ruling on the prayer and fasting of a woman who sees only yellowish discharge during her menstrual period, after inserting an IUD?

Scholars have differed on the issue of yellowish and brownish discharges, and the relied-upon opinion is that of the Hanbalis, who state that yellowish and brownish discharges are considered menstruation if a woman sees them during her regular period.

Therefore, your wife must stop praying and make up for the days she fasted in Ramadan. However, if she follows someone who issues a different fatwa, there is no harm upon her.