I've posted this in the past, so bear with me , those of tyou who have heard it already...
I got my period bak very early considering how exclusively breastfed DD was (darn!) and privacy in the bathroom is not accepted by my Velcro child. As long as I can remember, we've talked about mommy's mesnes and moontime, and I have told her that someday she too will have a moontime... (which she thinks is cool because she's got this "thing" about the moon. I think she thinks she's Artemis, the moon goddess)
At first, there were no questions about this. But in the past year she has asked for more specific info, like why does it look like blood and does it hurt, etc. She loves her birth story and knows babies grow inside their mommas in the womb. Well, I tell her that every month I lay an egg (like a chicken, which makes her laugh) and like a chicken, I like to lay my egg in a soft nest. So God (we're a pretty God-talking family, but one could substitute nature) has made my body so that every month I "build" a nest. But since it's inside my body and not up in a tree, my body uses the materials on hand: blood and tissues, whatever... Then, if the egg isn't going to grow into a baby, the nest falls apart and comes out through my vagina, just like the baby would if it DID become a baby.
God, I wish my mom had told me this so I wouldn't have been convinced I was dying the day I got my first period!
Of course, one of these months, she's gonna ask about the daddy's role. I'm still working on that talk