- Immune thrombocytopenia (ITP) in pregnant women can cause neonatal thrombocytopenia by transport of anti platelet autoantibodies across the placenta. Usually, infant's platelet count normalizes within two months. We observed neonatal thrombocytopenia that persisted more than four months and disappeared following discontinuation of breastfeeding. The aim of our study was to discern whether breast milk of ITP mothers contained anti platelet antibodies causing persistent thrombocytopenia. We collected milk samples from 3 groups of women: ITP - 7 women who had ITP during the pregnancy, R-ITP - 6 women who recovered from ITP before pregnancy and 9 healthy controls. We found increased levels of anti-platelet antibodies of the immunoglobulin A type in the milk of ITP patients compared to the other 2 groups. Similar increase was demonstrated for antibodies binding to αIIbβ3 expressed in cultured cells. Thus, transfer of anti-platelet antibodies from ITP mothers by breastfeeding can be associated with persistent neonatal thrombocytopenia. Copyright © 2015 American Society of Hematology.