A woman who wore a C cup bra prior to her pregnancy may need to buy an F cup or larger bra while nursing.[2] A woman's torso also grows and her bra band size may increase one or two sizes.[3][4] An average of 80% of women wear the wrong bra size,[5] and mothers who are preparing to nurse can benefit from a professional bra fitting from a lactation consultant.[4] Once the baby is born and about 50 to 73 hours after birth, the mother will experience her breasts filling with milk (sometimes referred to as “milk coming in”) and at that point changes in the breast happen very quickly. Once lactation begins, the woman's breasts swell significantly and can feel achy, lumpy and heavy (which is referred to as engorgement). Her breasts may increase again in size, by another 1 or 2 cup sizes,[3][4] and individual breast size can vary daily or for longer periods depending on how much the infant nurses from each breast.