Stretch marks are part of a condition affecting the skin, and are commonly found in the population. These white, smooth, linear lesions can be found anywhere on the body and are related to stretching of the skin. The most common sites to be affected by stretch marks include the breasts, buttocks, thighs and lateral abdomen. Stretch marks appear to be a type of scarring that occurs in the dermal layer of the skin, as a result of an altered healing response and replacement of collagen.
Depending on the race and age of the population studied, the prevalence of stretch marks has been reported to range from 50% to 90%. Many women develop stretch marks during their first pregnancy. One study demonstrated that 43% of the women enrolled developed stretch marks before 24 weeks of gestation. It is unknown why some women are not affected; a recent study, strongly suggests that your family history and genetics may play a role.