Some young women find that their appearance changes after pregnancy. Not only do dark brown spots or patches appear on the face, but pigmentation and stretch marks can also appear on the abdomen, chest, thighs and other parts of the body. Why is this happening? Causes of stretch marks: Medical research tells us that the hormones in the body are mainly responsible for changes in the appearance of pregnant women during pregnancy. In early pregnancy, hormones are produced primarily by the corpus luteum of the ovaries. Later, when the demand for hormones increases, the placenta takes the lead in secreting hormones. At the same time, the thyroid, pancreas,