Idiopathic myelofibrosis is a rare myeloproliferative disorder characterized by excessive accumulation of connective tissue in the bone marrow in association with anemia, splenomegaly, and extramedullary hematopoiesis. The cause of this disease is unknown, and the prognosis is generally poor. To our knowledge, this is the first case report of a patient with idiopathic myelofibrosis who carried a term pregnancy. In spite of the increased perinatal risks, a favorable outcome was possible with close antepartum surveillance.