My very polite son asked me what SEX was in the busy waiting room of the doctor's office and I almost had a heart attack! My mind was racing. I was thinking..."You have to ask me this NOW? HERE?"
It turned out he was asking because it asked for "SEX" on the paperwork I was filling out. What did the M and the F stand for?
I said, "I'm a girl, so F means female. That is my sex. You're a boy, so M means male. That is your sex".
That's all he wanted to know.
Whew.
I would ask your daughter what she thinks or what she's heard and take it from there. You can give information without being overly graphic.
You know, kids who grow up on farms or raising animals just tend to have an innate understanding of these things. It's just part of life that there are seasons for baby animals to be born, etc.
The main thing is to not psyche yourself out. You don't have to focus on what men and women do. We're mammals. You can teach kids about reproduction from that standpoint without the bow-chicka-wow-wow.
It also helps to explain why girls develop breasts and why they have periods.
You don't have to give too much "adult" information.
Just my opinion and good luck!