During pregnancy, the mother undergoes changes to sustain and enable normal growth and development of the fetus. Common physiological changes include linea nigra, fibroepithelial polyps, striae, spider angioma, palmar erythema and pruritis gravidarum. However, there are some changes that are purely pathological, and these are termed the pregnancy-specific dermatoses (PSDs). The PSDs occur during pregnancy or in the immediate postpartum period. They do not include the various benign conditions or pre-existing dermatoses and tumours that may present or worsen with pregnancy. They do include a number of distinct and identifiable conditions: atopic eruption of pregnancy (AEP), polymorphic eruption of pregnancy (PEP), intrahepatic cholestasis of pregnancy (ICP) and pemphigoid gestationis (PG). These are a heterogeneous group of skin conditions characterized by pruritis and inflammatory changes. In addition, pruritis gravidarum is sometimes considered pathophysiological and thus part of this group, rather than a physiological process. Each of these conditions has a distinct, but not fully understood, pathogenesis. The mechanisms leading to PSD may be a reflection on the hormonal and immunological changes associated with pregnancy. AEP and PEP are benign conditions, and although they can cause distress to the mother, they are otherwise minor. However, ICP and PG are more serious conditions, and both carry the potential for serious risks to both the mother and the fetus. Thus, the pathophysiology of these latter two conditions is considered in more detail in the following article.