During pregnancy, changes in the skin, hair and nails are common. The correct diagnosis and treatment of these conditions during pregnancy are essential to ensure the health of mom and baby, experts say.

"The body experiences profound adjustments during pregnancy, which make pregnant women susceptible to changes of the skin, hair and nails," said Dr. George Kroumpouzos, a dermatologist and co-author of "Dermatoses of Pregnancy," published in the Journal of the American Academy of Dermatology.

"A careful history and thorough examination by a dermatologist can relieve anxiety about the nature of these skin conditions and the possible fetal or maternal risks associated with them."

Some things you should know, he said:

Pigmentary Changes

Hyperpigmentation is common during pregnancy, affecting more than 90 percent of pregnant women. Hyperpigmentation is a skin disorder in which dark spots appear on the skin. This benign condition is attributed to an overproduction of melanin, a natural substance that gives color to the hair, skin and iris. Normally hyperpigmented areas, such as the breasts and nipples, genital skin and inner thighs, may become darker in pregnancy. Freckles, nevi and scars may appear darker as well.

This condition disappears in the months following pregnancy.

Melasma or chloasma, known as the "mask of pregnancy," has been reported in up to 70 percent of pregnant women. This common condition causes an increase of pigmentation that occurs almost exclusively in sun-exposed areas.

"Melasma presents in three facial patterns," explained Kroumpouzos, an instructor in the Department of Dermatology at Harvard University, Boston. "The centro-facial pattern involves the cheeks, forehead, upper lip, nose and chin. The malar pattern involves the cheeks and nose, and the mandibular pattern involves the side of the cheeks and jawline."

Melasma also can develop on the forearms. Dermatologists encourage the use of proper sunscreen to prevent this condition; they also recommend treatment with topical corticosteroids, bleaching agents, chemical peels or tretinoin. Most cases of melasma resolve after pregnancy.

Hair and Nail Changes

"Pregnancy affects every area of the skin, including hair and nails. Undesirable changes may occur that leave pregnant women feeling anxious," said Kroumpouzos. "A discussion with a dermatologist can put a woman at ease regarding these changes."

Hirsutism, a condition in which a woman grows hair in areas where only a man would -- such as the face or chest -- can be triggered by the endocrine changes of pregnancy. This condition usually regresses within six months following birth.

Telogen effluvium is the excess shedding of hair that usually occurs one to five months following pregnancy. During pregnancy, an increased percentage of scalp hairs go into the resting phase that is part of the normal growth-loss cycle of scalp hair. After pregnancy, these hairs begin to fall out and thin. However, this condition does not cause permanent hair loss or obvious bald patches. Telogen effluvium resolves slowly, beginning six to 12 weeks postpartum. There is no medical treatment available.

Nails, like hair, can change noticeably during pregnancy. Some women find that their nails tend to split and break more easily during pregnancy. Like the changes in hair, nail changes aren't permanent.

Skin Conditions

Pruritic urticarial papules and plaques of pregancy (PUPPP) is the most common skin condition of pregnancy, occuring in the third trimester. It is characterized by small red bumps and hives and, when severe, the bumps form large patches. This rash usually develops on the abdomen and spreads to the thighs, buttocks, breasts and arms.

Slight itching from PUPPP may cause mild discomfort. However, PUPPP does disappear after delivery. Anti-itching topical medications, antihistamines and topical corticosteroids can be used to control the itching.

Stretch marks develop in more than 90 percent of women during the sixth and seventh months of pregnancy. These occur in response to the pulling and stretching forces in the underlying layers of skin during gestation. They most often occur as pink or purple bands on the abdomen and sometimes on the breasts and thighs. While common in Caucasian women, stretch marks are uncommon in African-American women.

"Exercise and use of lotions or creams with alpa hydroxy acids can be used to prevent striae," said Kroumpouzos. "The use of retinoid products can also be used to fade the marks, but usually some silvery discoloration remains."

Although not related to the herpes virus, herpes gestationis, also known as pemphigoid gestationis, is the most well-defined dermatosis of pregnancy and the most important to diagnose.

Herpes gestationis is characterized by blisters on the abdomen during the second trimester; in severe cases, the blisters can be very expansive. Herpes gestationis usually resolves during the later parts of pregnancy and will flare at the time of delivery. The condition usually disappears in the weeks and months following delivery and may reappear with menses or with subsequent use of oral contraceptives.

Treatment includes oral or topical corticosteroids.

Prurigo of pregnancy consists of very itchy, tiny bumps that appear almost anywhere on the skin. This condition can appear during any trimester, with a few bumps appearing and increasing in number each day. It usually remains for several months and may even persist postpartum. Reoccurrence during subsequent pregnancies is variable. Treatment usually includes topical corticosteroids and antihistamines.

Skin Diseases Affected

"Pregnant women with certain skin diseases are more likely to experience an aggravation or, less often, an improvement in their condition," said Kroumpouzos.

Women with atopic dermatitis, a chronic skin disease causing itchy, irritating skin lesions, are likely to see a worsening of the condition during pregnancy. The condition also may develop for the first time during pregancy.

Psoriasis is more likely to improve than worsen during pregancy. Psoriasis is a chronic genetic skin disorder characterized by raised, thickened patches of red skin covered with silvery-white scales that can affect any part of the body. This improvement may be attributed to the high levels of interleukin-10 in pregnancy, a protein that is released by one cell to regulate the function of another.

"It's important for women to speak with their dermatologists if they notice any of these changes," said Kroumpouzos. "Though the origin of many of these conditions remains unknown, there are many treatment options available that will relieve the discomfort and anxiety, and lead to a more relaxed pregnancy."