What is the ruling on the prayer of a woman who uses birth control pills that lead to the discharge of blood similar to menstrual blood at the end of every month?

If blood appears after a period of purity and fifteen days have passed since that purity, then it is menstrual blood, and the woman must refrain from prayer and fasting because of it. However, if it appears before fifteen days have passed since the period of purity, then it is not considered menstrual blood, but rather blood of istihadah (non-menstrual vaginal bleeding).