My first question is why are you saving up for science? Not to give the game away, but focus on food! I think you are okay because having babies takes workers away from tasks in the earlier portions of the game.

Your villagers will breed until they die. I was originally worried about the same thing until I read a post that someone had a 75 year old have a baby! You just don't want your older villagers to die with a bunch of 7 year olds running around.