Purity: Delaying Prayer When Blood is Absent
Practical Laws of Islam as per the teachings of Ayatullah Sistani
Ruling 407:
If a mustaḥāḍah knows that from the time she started performing wuḍūʾ or ghusl no blood has come out, nor is it in the vagina, she can delay performing prayers until the time she knows she will not experience istiḥāḍah.
-Ayatullah Sistani, Practical Laws of Islam, Purification (Taharah)