Hyperpigmentation can be found in about 90 percent of the pregnancies. Women of darker complexion are more likely to manifest hyperpigmentation. The area around nipples, umbilicus, and peri-anal skin may darken, and the linea alba (light white line between the mid stomach and pubic area) becomes linea nigra (turns dark). Some women develop dark patches on the face. Most of these changes disappear after childbirth. It helps to protect the face from sun or use sunscreen. Best of luck with your pregnancy.