This report illustrates a case of portal vein thrombosis that developed in the second trimester of pregnancy. The patient did not have any of the known associations or predisposing factors for portal vein thrombosis or any past medical history of thrombosis or bleeding disorders. Antepartum and postpartum laboratory studies showed no evidence of a coagulation disorder; therefore, it seems that the sole cause of this thrombotic event was the hypercoagulable state of pregnancy.