Question: If a women has her menses for three weeks after having a child, when is it permissible for her to start fasting?

Answer: The time given for the Nifaas (that is, the flow of blood after delivery) is forty days. However, if a woman has seen the flow of blood for only three weeks after which it stopped, and she knows from her experience that it will not come again, then she can begin to fast from that time.


And Allah knows best.
Mufti Waseem Khan