Snapshot A 30-year-old G1P0 woman presents to her obstetrician with a new itchy rash. She is 36 weeks pregnant. The rash has been present for a week now with intense pruritus. She denies any other symptoms, including shortness of breath, swelling of the eyes, or fever. She denies any exposure to new medications or allergens. On physical exam, there are multiple erythematous urticarial plaques within the stretch marks on her abdomen. The umbilicus is spared. Introduction Pruritic urticarial papules and plaques of pregnancy (PUPPP) or polymorphic eruption of pregnancy (PEP) A self-limited pruritic inflammatory disorder of the skin occurring in the last trimester of pregnancy or immediately postpartum Epidemiology Common in primiparous women Common in women with multiple gestation pregnancies ETIOLOGY Pathogenesis largely unknown degree of skin stretch of abdomen may play a role Presentation Symptoms occurs in late third trimester or postpartum extremely pruritic, erythematous urticarial papules and plaques within striae on abdomen periumbilical sparing of rash can spread to extremities, chest, and back spares palms, soles, and face lasts 4-6 weeks, typically resolving within 2 weeks postpartum Evaluation Diagnosis is usually based on history and physical exam Skin biopsy only if diagnostic uncertainty perivascular and interstitial lymphocytic infiltrate with eosinophils No lab abnormalities Differential Diagnosis Pemphigoid gestationis Erythema multiforme Other drug reaction rash Treatment Initial therapy mid-to-high potency topical steroids If refractory systemic corticosteroids with quick taper Anti-histamines for pruritus Prognosis Resolves typically in 4-6 weeks or within 2 weeks postpartum No risk of fetal or maternal morbidity