Hormonal alterations contribute to the physiologic skin changes in pregnancy, which include hyperpigmentation and melasma, striae gravidarum and vascular phenomena, such as spiders, palmar erythema and varicosities. Hair, nails and sweat glands may also be affected. Dermatoses associated with pregnancy include herpes gestationis, impetigo herpetiformis, pruritic urticarial papules and plaques of pregnancy and papular dermatitis of pregnancy. Some skin tumors are affected by or are unique to pregnancy.