Enlargement of structures within the abdomen will lead to distention, a bulging contour. By far the most common cause of this is pregnancy. By the end of the third month, the pregnant uterus has grown out of the pelvic cavity and may be felt Just above the pelvic bones in the bladder region. By the sixth month, the pregnant uterus has reached the level of the umbilicus; by the ninth month, it is close to the lowermost portion of the breastbone.
The only comparable enlargement is that found with certain very large cysts of the ovary. In the course of such abdominal enlargement there may be a stretching and cracking of the connective tissue of the skin resulting in linear markings over the lower abdomen known as striae; these generally appear pink during pregnancy, but afterwards turn white. During a succeeding pregnancy new pink markings dispersed among the older ones may be seen. Neither abdominal supports nor other measures will prevent such markings. The number vary from individual to individual. There are some who never show striae, or in whom they are inconspicuous.