"Umm Habibah hint Jahsh sought a verdict from Allah's Messenger. She said 'I suffer from persistent bleeding such that I do not become pere. Shall I give up the Salat?' He said: 'No, that is only a blood vessel. So perform Ghusl then pray.' So she would perform Ghusl for each prayer."
Jami` at-Tirmidhi Book 1, Hadith 129