You have probably never noticed the pale line, called the linea alba, that runs from your belly button to the top of your pubic bone. It is usually the same color as your skin, but during pregnancy this line may darken (usually during your second trimester) and is then called a linea negra (Latin for "black line”). This darkening is caused by increases in estrogen and progesterone, which in turn step up production of the pigment melanin, a condition known as hyperpigmentation. Fair skinned women show linea negra less often than women with darker pigmentation. And some research suggests there may be a link between linea negra and insulin.
An old wives' tale claims that if your linea negra runs only to your navel, you are carrying a girl; but if it goes all the way up to the xiphoid (bottom-most part of the center of your ribcage), it's a boy.
There is no way to prevent or erase the linea negra. However, if it bothers you, here's what you can do:
Reduce pigment changes by protecting yourself from the sun and avoiding bleaching products.
Get enough folic acid. Folic acid deficiency may increase skin discoloration.
If the line bothers you, try covering it up with some concealing makeup.
Your linea negra will lighten within several months of your baby's birth, but for some women, it never completely disappears.