The linea nigra is a dark vertical line that usually appears on the abdomen during pregnancy, most commonly in the second trimester, and is caused by hormonal changes that increase melanin production in the skin. It is completely normal for its timing, length, and darkness to vary from person to person, depending on hormone levels and skin type. After delivery, the linea nigra typically fades gradually over a few months, although in some cases it may take longer to disappear completely. There is usually no need for treatment, but keeping skin hydrated, avoiding excessive sun exposure, and maintaining good nutrition may help the skin recover more evenly over time.