My wife is pregnant, but I know am not responsible for it (fiction)

Five years after our marriage, we were blessed with two children, a boy and a girl, and since then we have been living peacefuly.
My wife is a God fearing woman so i trust her on anything she is doing. Last year, I traveled for a business meeting, on my way back we had an accident which claimed no life but i sustain an injury. When i returned home i visited my personal doctor for a checkup. I got a sad news, i became impotence as a result of the accident which means i wont be able to have another kid again.
I was afraid to tell my wife about it so she won't be sad. Few weeks ago, she came to me with a good news that she is two months pregnant, but i know am not responsible for it.

Should i open up to my wife the truth that am impotence or just accept the pregnancy. Please your advice needed.