Q: I have learnt that as a precaution when a women has her periods, the area from the navel to the knee should be covered in front of the husband, so that he is not inclined sexually. Is it haraam if any area becomes exposed, or if the husband touches skin to skin any part of the area?
A: It is not right for the husband to touch these areas. He must exercise precaution.
And Allah Ta’ala (الله تعالى) knows best.
فيجوز الاستمتاع بالسرة وما فوقها والركبة وما تحتها ولو بلا حائل وكذا بما بينهما بحائل بغير الوطء ولو تلطخ دما ( رد المحتار 1/292)