The Changing of a Fixed Cycle

1. If a mu’taadah – one who has a routine or fixed cycle in haidh or nifaas – bleeds the set time and amount of her days, then it is obvious that her cycle remains unchanged.
2. If, however, she experiences something different, such as the time or number of days, or both the time and amount being different, then in this case sometimes the cycle changes and sometimes not.
3. In her case, the question is whether her aadat (cycle) has changed or not?
4. If here aadat has not changed then her haidh or nifaas remains unchanged.
5. For example, if the bleeding in haidh goes beyond 10 days, or beyond 40 days in nifaas, then her haidh and nifaas will remain whatever her aadat is.
6. The remainder will be isitihaadhah.
7. If the bleeding was not more than 10 days in haidh and not more than 40 days in nifaas, but more or less than her aadat, then her aadat has changed, that is her set number of days have changed.

(Manhalul Waarideen)