Postnatal discharge usually lasts for 4o days and women are not allowed to pray or fast during this duration. It doesn’t have a minimum duration but if she is clean before 40 days she can take a bath and offer prayers.
Postnatal bleeding: This refers to the blood discharged by women after childbirth.
There is no minimum period for postnatal bleeding, and therefore it depends on whether the discharge stops or continues. Its maximum duration is usually 40 days, however with some women it takes longer to finish. Al-Tirmidhi said that all scholars among the Prophet’s (peace be upon him) Companions and their successors agreed that a woman does not pray for 40 days after childbirth, unless she becomes clean before that, and in this case she takes a bath and offer her prayers normally.
:Umm Salamah reports
‘During the Prophet’s (peace be upon him) lifetime, a woman who has given birth used to stay 40 days.’
Related by Ahmad, hadith No. 26,584; Abu Dawud, hadith No. 312; al-Tirmidhi, hadith No. 139; Ibn Majah, hadith No. 648
The same rules regarding menstruation apply to postnatal discharge.