Purity: Duration of Nifas

Practical Laws of Islam as per the teachings of Ayatullah Sistani

Ruling 500:

It is possible that the blood of nifās lasts no longer than a moment; however, it is not considered to be nifās if the blood continues for more than ten days.

-Ayatullah Sistani, Practical Laws of Islam, Purification (Taharah)