Should Women Fast If There Is No Postpartum Bleeding?
Question

There is a woman who gave birth 22 days ago, but she does not have any postpartum bleeding. Should she pray? Or should she wait for forty days?
Praise be to Allah.Ruling on fasting if there is no postpartum bleeding
Nifas (postpartum bleeding) refers to the blood that comes out of the uterus because of giving birth. 
If the birth took place without any bleeding -- which is very rare -- then the woman is not regarded as being in nifas and she is not subject to the same rulings as women who are in nifas, because the ruling depends on the presence of blood. 
Ibn Qudamah al-Maqdisi said: If she gives birth and does not see any blood, then she is pure (tahir) and not in nifas, because nifas is blood, and there is no blood in this case. End quote. Al-Mughni, 1/429 
Ibn Hajar al-Haytami said: 
“If a woman gives birth and does not see any blood, then there is no nifas for her at all, and if she does ghusl, she comes under the same rulings as women who are pure (tahir) in all aspects.”(Al-Fatawa al-Fiqhiyyah al-Kubra, 1/358) 
In al-Mawsu‘ah al-Fiqhiyyah (41/15) it says: 
“If the birth was free of blood or there was no bleeding, such as if the infant came out dry, then she is pure (tahir) and there is no nifas for her, because nifas is blood, and there is no blood in this case.”
The scholars of the Standing Committee for Issuing Fatwas were asked: Some women experience difficulties in giving birth and they have to give birth by means of a Caesarian section, in which case the child does not come out through the vagina. What is the ruling on these women in Shari`ah, with regard to the bleeding of nifas? 
They replied: 
“They come under the same ruling as women who are in nifas: if the woman sees blood, she should refrain (from prayer etc.) until she becomes pure, and if she does not see any blood, then she should fast and pray like all other women who are pure (tahir).” (Fatawa al-Lajnah al-Daimah, 2/420) 
Is ghusl obligatory if there is no postpartum bleeding?
The scholars differed as to whether ghusl is obligatory in this case. 
It was said that she does not have to do ghusl , because Islam only requires it of women who are in nifas, and in this case the woman is not in nifas in any way. This is the view of the Malikis and Hanbalis. (See: al-Mughni, 1/429; al-Mawsu‘ah al-Fiqhiyyah, 14/51) 
Shaykh Ibn ‘Uthaymin (may Allah have mercy on him) favoured this view, and said: 
“If a woman gives birth and does not see any blood, which is very rare, in this case she should not refrain (from prayer and so on) for the period of nifas. If she gives birth at sunrise and the time for Zuhr begins and she did not see any blood, then she does not have to do ghusl; rather she should do wudu and pray.” (Al-Sharh al-Mumti‘, 1/281) 
And it was said that she does have to do ghusl, because giving birth is usually a cause of nifas which makes ghusl obligatory, so giving birth should make ghusl obligatory too. This is the view of the Shafi`is and is the view favoured by the scholars of the Standing Committee for Issuing Fatwas, who said: 
“If a pregnant woman gives birth and no blood comes out, then she has to do ghusl and pray and fast, and her husband may have intercourse with her after she does ghusl, because what usually happens in the case of childbirth is that blood comes out, even if it is a little, with the baby or straight afterwards.”(Fatawa al-Lajnah al-Daimah, 5/421) 
In order to be on the safe side, she should do ghusl so as to avoid an area in which there is a difference of opinion among the scholars. 
Should women fast if postpartum bleeding stops before 40 days?
If she bleeds for several days, then the bleeding stops , she has to do ghusl and pray and fast, even if that is before forty days have passed since giving birth. There is scholarly consensus on this point, because there is no minimum limit for nifas. If the bleeding resumes within the 40 day period , then this is nifas; and whatever goes beyond the 40 days is istihadah (irregular bleeding) which does not prevent her from praying and fasting. 
And Allah knows best.