Clean period between Nifaas and Haidh

In principle, the maximum period of Nifaas (post-natal bleeding) is forty days while there is no minimum limit to it. The same rules that apply to a women in Haidh (menstruation) apply to a woman in Nifaas (post-natal bleeding).

In the enquired situation, if a woman experiences Nifaas (post-natal bleeding) for forty days, she will have to wait for a minimum period of fifteen days before she counts her next Haidh cycle. Therefore, since your wife has experienced Nifaas (post-natal bleeding) for forty days, she will have to wait for a minimum period of fifteen days before she counts her next Haidh cycle. If she spots any blood during the fifteen days period, it would be regarded as Istihaadhah (irregular discharge) and the laws of Istihaadhah will apply. (Shaami 1/285)

And Allah Ta’ala Knows Best