The reality: About half of all pregnant women develop pink or reddish streaks called stretch marks or striae on the breasts, hips, or abdomen. Some women may end up with a thin brown line that runs from the belly button to the pubic bone or irregular brownish patches on the forehead, nose, upper lip, and cheeks. Moles may appear larger and darker; some women develop tiny, flesh-colored flaps of skin called skin tags on their neck and underarms.
The reason: Stretch marks occur when the elastic fibers in skin stretch and rupture due to weight gain. If you already have some stretch marks from growing hips during puberty, you're probably in for more when you're expecting. And because pregnancy hormones increase the body's production of melanin, a pigment that tints the skin, some women may develop chloasma (also known as melasma or the mask of pregnancy) on their face and/or linea nigra, the darkening of the hard-to-see white line called linea alba, which runs down your midsection. Melanin is also responsible for your moles' altered appearance, and skin tags occur from extra skin growth that may happen during pregnancy.
The relief: The good news? All of these marks, splotches, and lines fade, although for some women they may never completely disappear. Gaining weight slowly can reduce your chances of getting stretch marks, and liberal use of sunscreen can help minimize pigment changes. Moles should return to normal. If not, see your doctor, as some mole changes indicate skin cancer. Skin tags will disappear or can be easily removed by your doctor.