Final answer:
The dark brown line on your stomach during pregnancy is called the linea nigra, caused by increased melanocyte-stimulating hormone and melanin production. It is a normal change during pregnancy and should fade after childbirth. Other skin changes like stretch marks and chloasma are also common.
Step-by-step explanation:
The dark brown line running down your stomach during pregnancy is called the linea nigra. This is a common occurrence where an increase in melanocyte-stimulating hormone, along with estrogens, prompts an increase in melanin production, leading to the formation of the dark line from your belly button down to your pubis. The linea nigra typically forms during pregnancy and can persist for a few weeks after childbirth before fading away.
Other integumentary system changes during pregnancy include striae, commonly known as stretch marks, which are caused by the stretching of the dermis to accommodate the growing uterus and other changes in the body. You might also notice darkening of the areolae, chloasma, or 'mask of pregnancy,' which is the appearance of blotchy brown patches of skin on the face.
While many of these skin changes are a normal part of pregnancy, they usually diminish or disappear after the baby is born. Rest assured that the linea nigra is a temporary change and doesn't require any specific treatment.