What is the ruling on the blood that comes from a woman who has had a miscarriage?

According to the Hanafi and Hanbali schools, the blood that comes from a woman who miscarries a fetus with developed limbs such as hands, feet, or fingers is considered postpartum (nifas) blood. If the miscarriage occurs before such limbs have formed, the blood is regarded as irregular (istihada) bleeding. (See Marghinani, al-Hidaya, 1/35; Ibn Qudama, al-Mughni, 1/253) According to the Shafi'i and Maliki schools, any miscarriage, regardless of the stage, is a cause for postpartum bleeding. (Ramli, Nihayat al-Muhtaj, 1/323; Dusuqi, Hashiya, 1/174)

It should be noted that these rulings were given at a time when it could only be determined whether what exited the womb was a fetus if limbs such as hands and feet were visible. (See Kasani, Bada'i, 1/43) Nowadays, since it is possible to determine whether what was miscarried is a fetus at any stage, it is appropriate to act accordingly. Therefore, if it is known that what was miscarried is a fetus, regardless of whether its organs are formed, the blood seen after the miscarriage should be considered postpartum bleeding.

Source: T.C. Diyanet İşleri Başkanlığı, Din İşleri Yüksek Kurulu