Stretch marks 

Stretch marks or striae also called striae distensae in scientific language, are kind of small cracks similar to soft scars formed on the skin. They appear when the skin is subjected to excessive stretching, by atrophy of the elastic network. They can decrease over time, but will never completely disappear. Stretch marks are often due to excessive stretching, too fast, and too rough skin. Pregnancy or significant weight gain, a growth spurt at puberty, but also weight or hormone replacement therapy are all cases where stretch marks can occur. The stretch marks appeared on his stomach or on all parts of the body during pregnancy are called striae gravidarum.