After a woman is pregnant, with the growth and development of the fetus, the uterus will gradually expand, which will cause long-term oppression on the abdominal skin and make the abdominal skin tissue bigger. Due to the poor venous return in the body, there are different degrees of edema in limbs, face and other parts, more water is produced in the tissue gap, and the skin is tight. After giving birth, although the abdomen has shrunk, due to long-term traction, the skin tissue elasticity is not enough, leading to skin relaxation.