 As a woman's breasts change in size during repeated pregnancies, the size of her breasts change as her mammary glands are engorged with milk and as she gains and loses weight with each pregnancy.In addition, when milk production stops (usually as a child is weaned), the voluminous mammary glands diminish in volume, but they still add bulk and firmness to the breast.A 2010 review found that weight gain during pregnancy and breastfeeding were not significant risk factors for ptosis.