Confessions: I gave my neighbour’s teenage daughter more than a lift to town

I am 32 and married with children but in serious trouble because I messed up with a young girl (18) from our estate and she is now pregnant. We became friends after I frequently gave her a lift to town then we had casual no-strings-attached sex on several occasions. She is now four months pregnant and she is asking me what she is going to tell her parents. I have tried to talk to her but she isn’t listening. I don’t love her and I can’t imagine losing my family because of this young and irresponsible girl. I think some neighbours are already suspecting something from the way they make funny statements at me and so it may just be a matter of time before this comes out. I don’t know what to do. Please advise.