I read this book about 20+ years ago when I was Junior High in the US. It was about this guy who fell in love with a woman from a fae race I believe? I honestly don’t remember that much about it except I think the cover had some art but was green in binding. They had some sort of huge struggle with a type of villain and they ended up together and pregnant. He thought it would be a normal 9 month pregnancy like for humans and her race actually had a 3 year gestation. Their baby was a girl who was very different and inquisitive and wasn’t a normal human child. That’s essentially all I remember.