It is permissible for menstruating women to stay in the place of Sa`i (between As-Safa and Al-Marwah) because this area is not part of Al-Masjid Al-Haram.
The eminent Muslim scholar Sheikh `Abdullah ibn Jibreen, member of the Standing Committee for Fatwa and Research in Saudi Arabia, states: “A menstruating woman can stay at the place of Sa`i because this area is not part of Al-Masjid Al-Haram. For this reason a woman who gets her period after making Tawaf (circumambulation of the Ka`bah) and before Sa`i can make Sa`i because, unlike Tawaf, purity is not a condition for Sa`i. Therefore, we can safely say that there is nothing wrong with a menstruating woman waiting for her family in the place of Sa`i. Moreover, she can make Sa`i between the hills of As-Safa and Al-Marwah while she has her menstrual period.”
Moreover, the late Sheikh Ibn `Uthaymeen, a prominent Saudi Muslim scholar (may Allah bless his soul), in response to a similar question, stated: “It is known that the place of Sa`i is not part of Al-Masjid Al-Haram, so there is a short fence separating it from the masjid. This is undoubtedly better for the Muslims because had the place of Sa`i been part of Al-Masjid Al-Haram, the woman who happens to get her period after performing Tawaf and before Sa`i would not be able to perform Sa`i. Yet, scholars agree that if a woman happens to get her period after Tawaf and before Sa`i, she can make Sa`i because the place of Sa`i is not part of Al-Masjid Al-Haram.”