I am so sorry this has happened to you it is an awful thing to happen and i know its not your fault but i do believe you are doing the right thing by this baby by terminating it now, who knows if you went to full term if it would suffer, how much it would suffer and that would be unbearable for you all.
Friends of mine had this happen to them aswell not sure if it was exactly the same thing but they found out at the 22 week scan that the skull hadn't formed properly, they had the baby a week later and held a funeral for all to attend who wanted to which was lovely to show that there was a life and a way of us showing them we supported them in their decision, it was a very sad time and i am happy to say they got through it together and after alot of debating even had another child, Make sure which i know you are doing to turn to each other. again i am really sorry and happy to hear you are not blaming yourself because its not your fault always rememeber that.