text: i,m emily i need to know if prenatal vitamins will make my breasts bigger so i can breast feed my baby when it   prenatal vitamins will not make your breasts bigger. the pregnancy hormones will make your breasts tender and sore and as you near the birth of your child, the breasts will swell with milk.  but prenatal vitamins have absolutely nothing to do with it. they are just large doses of the vitamins and minerals that your body needs because the baby is leeching what it needs to thrive and grow.