When women performed Hajj with Sayyidah Aishah (may Allah be pleased with her), she would fear that they might begin menstruating, so she would send them ahead on the Day of Sacrifice (Yawm al-Nahr) itself and they would perform the tawaf al-ifadah. If they began menstruating after that, she would not wait for them to become pure, but would depart with them while they were menstruating.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الحج / 9757