It is narrated from Sayyidah Aishah (may Allah be pleased with her) that Fatimah bint Abi Hubaysh (may Allah be pleased with her) came to the Prophet (peace and blessings be upon him) and said: I suffer from istihadah (prolonged bleeding) and I see blood. So he (peace and blessings be upon him) ordered her not to pray during the days of her menstruation, then, when the time of her purity came, to take a ritual bath (ghusl), then to perform ablution (wudu) for every prayer, and he said: "That is only a vein of yours."
Hadith Referenceالمعجم الكبير للطبراني / مسند النساء / 21265