وَإِذَا تَجَاوَزَ الدَّمُ عَلَى الْأَرْبَعِينَ، وَقَدْ كَانَتْ هَذِهِ الْمَرْأَةُ وَلَدَتْ قَبْلَ ذَلِكَ، وَلَهَا عَادَةٌ فِي النِّفَاسِ: رُدَّتْ إِلَى أَيَّامِ عَادَتِهَا.
Meaning: If bleeding exceeds forty days and the woman has previously given birth and has an established postnatal habit, she returns to the days of that habit.
As with menstruation, an established habit can govern nifas when bleeding exceeds the forty-day maximum.