Most mothers whose hormones are in the proper balance and who have normal breast development during puberty and pregnancy, will make plenty of milk for their baby.  Despite all their best efforts, there will be some mothers who will struggle with supply. I find that most mothers I work with, who struggle with supply, well they actually have one or more potential risk factors for low supply, however, they were just not made aware of it.  There are some very real factors that can put you at risk for not making enough milk and some you can know ahead of time and others take you by surprise.