So my 7 year old daughter and I went out for a girl's night. While we were having dinner, she was asking me all kinds of questions about various things. Then she says to me, "You might say I'm to young for this question, but how do babies get out of their mom's bellies?" I told her that I could give her the short version, but the long version would have to wait until she was older. She agreed. It was easy to explain because she has two brothers so she knows what a penis and a vagina are.
What was nice is that I told her that she could ask me anything. I would never lie to her, but sometimes I could only tell her the short version. I promised her that I would tell her the long version when she was older. She said, "I can live with that." I can live with that, too.