@Foofie,
My mom bought us a book and read it to us - I still remember it had a pink cover - and whenever we had a babysitter - my sisters and I would go get it and look at the little stick figure pictures having sex and laugh and laugh...I was about seven or eight I guess - old enough to read it myself and to my little sisters.
It didn't gross me out or upset or scare me in any way - she presented it very matter of factly- that was that.
With my kids - my son saw a package of sanitary napkins (sorry guys - hope this isn't too graphic) and asked me what they were and what they were for. He was about four. So I explained it - told him about the woman's monthly cycle - what it could lead to and when a woman would need the sanitary napkins and that she wouldn't if she were pregnant - which led to how most women get pregnant (these days there are all sorts of different ways) and/or acquire children- including adoption- which he WAS familiar with as his little sister had been adopted. Before this - he figured he must have been adopted too - he thought that was how ALL people got their new babies...he told me he was going to adopt because he believed that was the BEST way to get babies... I told him he might change his mind or his wife might have different ideas - but if he still wanted to later- that'd be great.
We even talked about birth control- and also breast feeding-
he's a very intelligent kid - so he just sort of nodded and soaked it all up.
My daughter saw a picture of me pregnant with her brother when she was about three. She said, 'Mommy - you were so fat...' I told her I was pregnant and looked fat because her brother as a baby had been growing in my belly.'
She said, 'Where's a picture of me growing in your belly?'
I told her I didn't have one because she grew in someone else's belly, but that woman wasn't able to care for her, so she chose us to.
She just nodded- I think it was harder for me than it was for her - up until then, I'd been the only mother she knew of - now I knew I was sharing that position in her thoughts with someone else.
Although she's sixteen now and has absolutely no interest in meeting her birth family - she says she's happy with me as her only mom- her dad as her only father - and her brother as her only sibling.
I went over the whole menstruation and sex thing with her fairly early - we talk about everything in my family. If they ask - I tell them the truth.
I think it's scarier to children if they feel that something is being kept secret from them - then it gains an air of mystery and maybe even forboding- instead of just being a part of life.
But every kid is different.