Estrogen is normally an important sex hormone in women’s bodies. It is a hormone secreted by women’s ovaries, which promotes the development of female sexual organs and secondary sexual characteristics, maintains the physical characteristics of women, and maintains normal reproductive functions. After pregnancy, estrogen also plays an important role in enlarging the breasts, preparing for breastfeeding after delivery, promoting the growth of the uterus, ensuring adequate blood supply to the uterus, and playing an important role in the development and maturation of the fetus. The secretion of estrogen also increases dramatically after pregnancy. The level of estrogen rises to 30-50 times the normal level at the beginning of pregnancy and reaches a climax at the end of pregnancy when estrogen secretion is about 1,000 times higher, and estrogen levels rapidly return to normal after delivery. Estrogen promotes the secretion of hormones related to skin pigmentation, causing pregnant women to experience darker nipples, a tendency to develop discoloration on the face, laxity of ligaments, back pain and even mood changes.