A 25 year old G1P0 woman at 30 weeks gestational age presents with intolerable itching, worse at night, mostly on the palms and soles of her feet. Exam only shows excoriations from scratching. The only laboratory abnormalities are elevated serum bile acid and alkaline phosphatase. GGT (gamma glutamyl transpeptidase) is normal. She has no history of liver disease and on ultrasound, biliary ducts and hepatic parenchyma appear normal.
Challenge: What's the diagnosis?