Does the blanket (duvet) and bedding used by a woman during her menstrual period become impure?

The default is that the blanket and bedding of a menstruating woman are pure, unless it is certain that they have been touched by impurity. As for mere doubt, it does not necessitate impurity. "The prescribed approach is to base the matter on the principle of istishab (presumption of continuity). If there is proof of impurity, we deem it impure; otherwise, it is not recommended to avoid using it merely based on the possibility of impurity."