4 year old DD just came bursting into the bathroom whilst I was putting on a sanitary towel. She asked what I was doing and then asked why. She already knows that babies are made from a mummy's special egg and a daddy's special seed then grow in their mummy's tummy. (She has 5 little cousins- we've had the 'where do babies come from' question a lot.) Anyway, I told her that when mummies and daddies don't want to have a baby, the mummy gets rid of the special egg by having a period and then a new one grows in its place. The sanitary towel takes the egg away. She accepted this and went on her merry way. DH thinks I have destroyed her innocence and should have lied. He also thinks that once I had told her this I should have told her that she must not talk about it to anyone else ever. 
He is a primary school teacher and apparently 'there is a reason we do not educate children about this until the age of 10'. I'm not going to lie to my dd and I thought id given an age appropriate explanation given the direct nature of her question. I'm doubting myself because dh is cross about it. Was I unreasonable?