Does vaginal bleeding due to surgery mean that one cannot fast?
Question

I gave birth two months ago but the bleeding of nifaas has not stopped until now. The radiographer found a piece of the placenta still inside the uterus, and I had an operation to remove it. This was after the first week of Ramadan had passed, but I did not fast until after the operation, even though the bleeding has not stopped. What should I do now? Is my fast valid? Can I have intercourse now, as the bleeding is very little since I did the operation?.
Praise be to Allah.The maximum length of nifaas (post-partum bleeding) is forty days, after which the woman is taahir (pure) and she may pray and fast and her husband may have intercourse with her, even if there is bleeding. This blood that comes after forty days is a haemorrhage, not nifaas. 
This has been discussed with evidence in the answer to question no. 106464 . 
Based on that, your fasting after doing the operation is valid, even if there is bleeding. 
You have to make up the first week of Ramadaan when you did not fast. 
With regard to the prayers that you did not offer after the forty days (of nifaas) ended, you do not have to make them up, in sha Allaah.  
See the answer to question no. 45648. 
And Allaah knows best.