Ref. No. 37 / 1111
In the name of Allah the most Gracious the most Merciful
The answer to your question is as follows:
A woman, who is in such a condition, should regard first 10 days of each month as her MC and rest 20 days of Istihaza. Her husband cannot have sex with his wife during 10 days of MC. In other 20 days – in spite of bleeding – he can have sex with her. He is also allowed to marry another woman, but due to istihaza – which is natural and Sharee excuse – he ought not to divorce the first wife.
فالعشرۃ من أول ما رأت حیض والعشرون بعدذلک طھرھا۔ بدائع ج1ص161
And Allah knows best
Darul Uloom Waqf Deoband