A woman’s breasts are the only organ in her body that undergoes more changes as she reaches adulthood. A leading expert once said, “The breast is an organ that keeps changing throughout a person’s life. It can change from small to large, or from large to small. It can change once in a few days, once in a month, or once in a few years, or once in a few decades in the case of a long person, which is unique among all organs in the human body. This change in size is unique among all organs in the human body and is influenced by the endocrine process, and the breast, as a target organ, is the organ most regulated by the endocrine process. Breast changes are not only changes in size, but also changes in the internal structure of the breast, which is unique to the breast. Changes in breast size are also inextricably linked to many breast diseases. (1) Breast changes during conjugal life: Before conjugal life, a large amount of venous blood flow to the breasts, the woman’s bilateral breast volume increases significantly during intercourse, accompanied by a mild feeling of swelling and pain. If the woman has reached orgasm at this time, after intercourse, the venous blood flow back to the breast quickly, the breast volume then returned to its original state. If the husband suffers from premature ejaculation or impotence during intercourse, and the wife fails to reach orgasm, the venous return to the breasts slows down and blood stagnates, resulting in the formation of lumps in the breasts, accompanied by obvious breast swelling and pain, which will lead to the occurrence of lobular hyperplasia in the breast over time. (2) Menstrual cycle breast changes: Since the week before the onset of menstruation. The level of estrogen in the body rises, and the level of progesterone also rises after ovulation. At this time, the breast ducts in the breast expand, the epithelium proliferates, and sodium and water retention occur, the breast tissue is obviously congested, the volume of the breast increases, and the tension also increases, accompanied by breast swelling and pain. Once menstruation occurs, the estrogen and progesterone levels drop significantly, and the breasts become smaller and softer, with a feeling of comfort in the breasts. These changes occur repeatedly in adult women during the non-pregnancy period. If estrogen levels remain high after menstruation and progesterone levels decline, poor breast regeneration occurs, which means lobular hyperplasia. (3) Changes in breast enlargement during pregnancy: Pregnancy and lactation are the most obvious periods in a woman’s life when her breast volume increases. Pregnancy breast enlargement is divided into five different stages of early, middle and late pregnancy. ①Early pregnancy. Due to the action of estrogen, the ducts of the breast grow rapidly and increase in number. Interlobular edema. The breasts grow in size bilaterally and are accompanied by a feeling of breast swelling and pain. ②Mid-pregnancy. Due to the increased secretion of progesterone, the terminal ducts expand and gradually form alveoli, capillaries in the interstitial mammary glands increase, and lymph nodes appear. The areola area is enlarged and the color of nipple and areola is dark brown. (3) Late pregnancy. Due to the high degree of bilateral breast enlargement, the superficial skin veins on the surface of the breast may become angry due to poor reflux. In late pregnancy, due to the combined effect of estrogen and progesterone, the glandular ducts increase and the glandular alveoli become even larger. The changes in the breasts during pregnancy are regulated by a variety of hormones and mothers-to-be should be reminded that. If there is a fibroadenoma or some other benign lesion in the breast prior to pregnancy, these women are advised to have it surgically removed or medically treated before pregnancy. It is well documented that if a “root of trouble” is planted in the breast before pregnancy, the hormonal changes that occur during pregnancy may cause these benign lesions to become malignant. Therefore, it is completely necessary to cure the benign breast lesions before pregnancy, so don’t miss out on the big picture. (4) Breast size changes during lactation: After delivery, estrogen and progesterone decrease significantly, while prolactin levels increase and milk has begun to be secreted. At this time has entered the lactation period, bilateral breasts are filled with milk, its volume is highly increased, the breast can be more than 1 times larger than the original breast. The breasts may become swollen and painful, and sometimes hard nodes may appear. Poor emptying of the breast during lactation, poor milk discharge from the milk ducts, or cracked nipples can lead to acute mastitis, and if not treated in time, can lead to the formation of breast abscesses.