A 36-week pregnant woman was diagnosed with acute lymphoblastic leukaemia. Delivery was initiated prematurely, and a healthy child was born. Cord blood and peripheral blood samples from the neonate (obtained at 6 weeks, 3 months and 6 months) were analysed for the presence of minimal residual disease by polymerase chain reaction analysis of a leukaemia-specific IGH gene rearrangement and the E2A–PBX1 fusion gene transcript. In the cord blood sample, a tumour load of ≈ 4 × 10−4 was found, whereas all later blood samples were negative. Our data indicate that the maternal leukaemic cells did not engraft in the neonate.