Breasts will not be swollen and painful in the first 1-7 days of pregnancy. Early pregnancy due to the rise of estrogen, some pregnant women consciously breast swelling and pain, there may be a gradual increase in the volume of the breast, the veins show, nipple areola color deepening, dark brown nodules around the areola, nipple enlargement and other manifestations, which generally appear in about 4 weeks of pregnancy, just pregnant will not be obvious breast swelling and pain. The main reason for breast swelling and pain is that estrogen secretion increases to stimulate the development of mammary ducts, progesterone secretion increases to stimulate the development of mammary follicles, in addition to pituitary prolactin, insulin, cortisol. Human placenta lactogen and other hormones involved. If you feel uncomfortable, you can relieve the swelling and pain by massaging and wearing loose underwear.