The obligation to continue considering menstruation until purification, even if a brief period of purity intervenes

A woman had an IUD inserted, and her usual period before the procedure was seven days. After the procedure, her cycle increased to ten days. It is known that on the seventh day, the flow of blood decreases, and on the eighth and ninth days, the flow of blood becomes heavy, and then it stops after the tenth day?
She continues [considering it menstruation] until she is purified.

The questioner: Is it part of her cycle?The Shaykh: Because this IUD changes the custom; because it narrows the outlets of the blood, and the blood becomes stagnant, so the duration becomes longer.