Background and objectives: Blood transfusion has been shown to be a risk factor for non-Hodgkin's lymphoma (NHL).
Materials and methods: In a cohort of 77,928 women with bleeding complications at delivery in the period of 1973-1986, subsequent NHL cases were identified and the number was compared with the number expected from national incidence rates. In a case-control study the proportion of transfused NHL cases was compared with the proportion of transfused controls.
Results: The observed number of NHL in the cohort was 18 versus 22.0 expected. Information on transfusion was obtained for 15 of the NHL cases and none (0%) was transfused versus 32 out of 136 controls (23%).
Conclusions: Blood transfusion at delivery is not a risk factor for NHL. The immune tolerance induced by pregnancy may reduce the risk of NHL associated with the transfusion of allogeneic blood cells.