Breast Changes in Pregnancy
It is not typical to have a breast mass while pregnant, but some can actually be large enough to distort the breast and make one size larger than the other, that calls for immediate gyno visits.. Most women are asymmetrical, but breast changes will be similar, your overall bra size will change, but it wouldn't be typical to need bigger cup on one side. Pregnancy hormones will enhance the development of the structures at the ends of the lobules that will eventually secrete the milk. In most women most of the change, or growth, or enlargement, of the breasts are due to this process of developing the mild producing structures. by mid pregnancy most of the milk production apparatus is set, and so most women will have some bra size change by then. Breasts themselves do have a lot of fat tissue, women who gain extra weight will probably gain a bra cup size or two on top of normal pregnancy growth, just from that extra weight. Bra changes due to excess weight gain can happen as early as the late first trimester, but is more typical in the early third trimester. the ligaments of support will stretch as the breast changes and the amount of stretching will determine if any shape changes occur. Just before labor there is a trigger to begin milk production, and the tissue begins to rapidly grow (on a microscopic level!). Thus as milk comes in there is enlargement of the breast post partum that can begin to or three days or up to a week after delivery. Women who are having their first will proceed more slowly than they will in subsequent pregnancies. Prolactin is our milk hormone, but it's an odd one. Women with pituitary glands that over produce or under produce prolactin can still lactate, and after having children the pituitary gland has significantly decreased prolactin production. We don't know the reason, nor do we completely understand the effects of this on the breast. Post partum there is cellular death of the extra breast tissue, but that won't affect mild production either. Early after delivery you cannot produce milk if you don't lactate, but after that phase the breasts can get very small and keep producing breast milk. In short, all women will have breast development in pregnancy, they will begin the sequence of mild production just before labor, they will have some enlargement of the breast due to weight changes, and they will have reversal of this process at some point post partum, depending upon whether and how long they breastfeed. Most women will gain in cup size of their bra, but wieght changes will make they need to also go up in chest size measurements. There is no predicting changes exactly, and some women retain most of their breast enlargement, and some women involute so completely they lose breast tissue they will never regain.