awkward

my manager pulls me aside today and asks me if I would have his baby if his girl couldn't I felt very uncomfortable and I had so many questions as to why he would ask me that. First were not even close at all and I'm trying no to think much of it and forget he asked me. Thank god other co workers came into the office before I can say anything. He knows I'm in a relationship too and I'm only 18.. any advice on what I should do or forget about it?