Do you give your Sim children plastic surgery if they don't look pretty enough for you?
I know some players like their Sims to be perfect and I've seen even children been given bigger eyes, poutier lips and their bodies made skinnier etc. I've even seen this done on 100 baby challenge ki...
I always leave my sim children as they naturally are, but maybe if there was something about them that really bothered me I would change it when they became young adults, but never as children.