If you have additional questions about discussing sexuality with your children, you may want to check the following section of our site: http://www.education.com/reference/topic/TeenYears_TeenDatingAndSex/. I know that the headline indicates that this section is about "teen dating and sexuality", but there are many articles relevant to younger children, as well.
Good luck and kudos to you for taking on this important issue with such seriousness and intent!
Laura Compian, Ph.D.
I also feel that it would be wise to wait a bit. It won't hurt them to wait till they are able to comprehend some emotional aspects of sex ed. It would probably be better to wait for that reason as well. So that the child gets the moral and the biological at the same time. It may be the reason for some persons who can seperate the two ( sex from Emotion) with little worry. This makes me worry : )))
I am studing to be a health teacher, and the best advice I can give is to keep it age appropriate. There is no need to have "sex talks" with her at this age, but by calling body parts by the correct names is a good start. When my daughters were that age I waited until they asked questions. I answered them honestly, but simply. They let me know when they had heard enough.
I wouldn't want my 4 year old knowing about sex!, I would prefer to wait until my child was older say 11 or so (secondary school age) before telling them about that. Although if I had a daughter I might talk to her about periods at 9 or so (girls begin puberty from age 9 upwards). So why not let your child enjoy their innocence and childhood for a few more years yet, after 4 is way before any body changes begin and they don't need to know about these things at that they are way to young.
there are many resources over the internet and to find the right one is really hard but i generally refer to http://factsd.com for all the facts, it has plenty of resources and information which would suffice