Polymorphic eruption of pregnancy (PEP), also known as pruritic urticarial papules and plaques of pregnancy (PUPPP), is the most common specific eruption of pregnancy. The etiology is unknown, but it may be related to skin distension. It is a benign condition that almost always begins in the third trimester of a first pregnancy or in the immediate postpartum period. This pruritic eruption develops in and around the abdominal striae and it may then spread to the extremities, chest, and back. It presents as erythematous or urticarial papules and plaques. Polymorphic clinical features are seen in around half of patients, including the development of eczematous papules and plaques, vesicles, and target lesions. Pruritus can be severe, leading to sleep disturbance.

PEP occurs in about 0.5% of pregnancies and is associated with a higher frequency of multiple gestation and significant intrapartum weight gain (with a higher degree of stretching of abdominal skin). Other risk factors include primiparity and Northern European descent. It is important to note that there is no association with adverse fetal or maternal outcomes. PEP is self-limiting and typically resolves within 4 weeks of rash onset, usually 2 weeks postpartum. Recurrence with subsequent pregnancies is uncommon.