Stretch marks are shriveled marks. Shrinking is a phenomenon that skin fibers break during pregnancy, fitness and sudden weight gain, showing red, white or purple stripes. It also includes obesity lines and motion cracks. In addition to the abdomen, there are body parts such as the inner and outer thighs, knees, buttocks, lumbosacral and so on.

The abdominal wall tissues of human body are skin, skin elastic fibers, subcutaneous fat layer, rectus abdominis composed of muscle fibers and tendons, preperitoneal fat layer and peritoneum from outside to inside. Under normal circumstances, the skin elastic fibers and rectus abdominis maintain certain elasticity and freely expand and contract within certain limits. When a woman is pregnant for more than 3 months, the enlarged uterus protrudes from the pelvic cavity and develops into the abdominal cavity, the abdomen begins to bulge, and the skin elastic fibers and abdominal muscles begin to elongate. It is more obvious after 6 months of pregnancy. At this time, the elastic fibers of the skin are gradually broken, and irregular longitudinal cracks of pink or purple appear on the surface of the abdominal skin. After production, the broken elastic fiber is gradually repaired, but it is difficult to restore to the previous state. The original cracks on the skin gradually faded and finally became silver stretch marks.