In the Name of Allah, Most Gracious, Most Merciful.
All praise and thanks are due to Allah, and peace and blessings be upon His Messenger.
In this fatwa:
The late prominent Saudi Muslim scholar, Sheikh Ibn `Uthaymeen, stated:
There is no specific period of time for post-partum bleeding. As long as there is blood, the woman should not pray nor fast and her husband should not have intercourse with her.
If a woman attains purity from this, even if before the completion of the forty days, such as after five or ten days, then she should pray and fast and her husband can have sexual intercourse with her.
This is because post-partum bleeding is something tangible and its rulings depend on its existence or absence. Thus, when there is blood, the rulings of post-partum bleeding apply and when there is no blood, all the rulings cease to apply.
However, if the blood lasts for more than sixty days, it would then be considered vaginal bleeding and not post-partum bleeding, and she should abandon the prayer only for the usual number of days of menstruation after the maximum sixty days, then perform ghusl and pray.
Almighty Allah knows best.