The lines on the belly after giving birth are called stretch marks, which are formed when the stretch fibers and collagen fibers of the skin are damaged or broken due to the expansion of the abdomen during pregnancy, and generally disappear gradually after giving birth, but some will always exist. The second is to replenish collagen and eat foods rich in protein and vitamins, which can speed up the recovery of broken elastic fibers. Then there are medical cosmetic treatments such as pulsed light and laser irradiation to lighten the stretch marks and accelerate the fading of the purple and red lines. There are also skin care products on the market that can help get rid of stretch marks by applying and massaging them.