A line from the navel to the abdomen occurs most often in women, especially in those who are pregnant or breastfeeding. The main clinical manifestation is a brown line from the abdomen to the belly button, with some difference in the color of the skin on both sides of the line, often without conscious symptoms. Its production is not yet particularly clear, but it is often considered to have a certain relationship with the body’s hormone, especially estrogen levels, but does not affect people’s lives, does not affect health, and generally does not require treatment.