The most common pigmentation change in pregnancy is called hyperpigmentation, or darkening of the skin. It is believed that higher levels of estrogen, progesterone, and melanocyte-stimulating hormone cause this skin darkening. The latter is a hormone that causes the pigment producing cells, or melanocytes, to make more melanin. Areas that were darker prior to pregnancy such as the areolae, nipples, genital skin, armpits, and inner thighs tend to get even darker. Sometimes a dark line, called linea nigra, forms on the abdomen. Other women experience a darkening of facial skin called melasma.
Hair and Nail Changes
Hair changes in pregnancy can vary from too much to too little. Many women notice more, darker hair on the face, arms, and legs. The same women may also notice a thinning of the hair on the scalp. This condition is known as telogen effluvium and is caused by a shift of these hairs to the telogen, or resting, phase. It is during the telogen phase that hairs are shed. This shedding may last from 1 to 5 months but may not stop until 15 months after delivery. Nail changes in pregnancy include brittleness, groove formation, or a separation of the nail from the end of the nail bed called onycholysis.
Interestingly, sweat gland function increases during pregnancy except on the palms, while sebaceous gland function decreases. Thyroid activity also increases, probably causing the increase in sweat gland activity. Diseases that affect the sweat glands such as miliaria (heat rash) and hyperhidrosis (excessive sweating) may get worse during pregnancy. While diseases that affect the sebaceous glands such as hidradenitis suppurativa, may improve during pregnancy. The sebaceous glands on the areolae, Montgomery's glands, enlarge during pregnancy and are noticeable as small brown bumps. Finally, the affect of pregnancy on acne is variable.