Structure of the skin:
The skin is composed of different layers. The deeper layer, the dermis, contains elastic and collagen fibers responsible for skin elasticity and firmness. They are formed like a net. While the elastic fibers are able to expand maximally up to approx. 150 per cent, a stretch of the collagen fibers is possible only to small extent (max. 5%).
Cause of stretch marks: Over-stretching of the dermis
In the first months of the pregnancy the tissue in the dermis loosens up. Starting with the third month the skin begins to stretch. The continuous and progressive stretching of the abdominal skin especially in the sixth and seventh month of pregnancy can damage and tear the elastic and collagen fibers in the dermis.