Four cases of relapse of acute lymphoblastic leukemia (ALL) in pregnancy have been reported previously. During the past 2 decades, ALL has become curable in a majority of children, many of whom have entered their reproductive years. Thus, additional occurrences of relapsing ALL during pregnancy can be anticipated. We present the fifth case in the English-language medical literature of recurrent ALL in pregnancy. A 20-year-old woman with ALL experienced a relapse during the third trimester of her first pregnancy. Reinduction therapy was started with vincristine and prednisone and the baby was delivered 3 weeks later. Umbilical cord blood was collected and stored. The patient then received intensive chemotherapy with whole body radiotherapy and autologous peripheral blood stem cell rescue. The ALL has been in second remission for 22 months. Our patient is the only current survivor of a relapse of ALL during pregnancy. In addition, the collection of umbilical cord blood from a pregnant woman with leukemia has not been reported previously.