Stretch marks are thin lines that are formed on the skin after a period of “intensive growth”, such as pregnancy, puberty, weight gain and weight loss. Pregnancy appears to be the main cause of stretch marks. According to a study published in the Journal of the American Academy of Dermatology, between 52% and 59% of pregnant women notice stretch marks during pregnancy. Some estimates are much higher, citing 90 percent.
Other factors in the development of stretch marks include
breast augmentation surgery
Medical conditions (e.g. Marfan syndrome and Cushing syndrome)
prolonged use of corticosteroids