Study alleges increased risk for males transfused with blood from a previously pregnant female ABC Talking Points

Tue, October 31, 2017 9:02 AM | Steve Bolton

Regarding the association of blood transfusion from female donors with and without a history of pregnancy with mortality among male and female transfusion recipients

October 2017 

  • JAMA (The Journal of the American Medical Association) has published a study by authors from the Netherlands that found increased mortality among patients transfused with blood associated with the gender and pregnancy history of the donor and the gender of the recipient. 
  • There was a 13 percent increase in death from all causes among males who received RBC transfusion from an ever-pregnant female donor compared to males receiving RBC units from male donors. This difference was slightly statistically significant. 
  • For males transfused from a never-pregnant female donor vs. male donors the risk of death was not higher. 
  • Rates in female recipients were identical regardless of donor gender or pregnancy status. 
  • The study design was retrospective and observational and studies with these design features are frequently found to be wrong when more rigorous studies are completed.1
  • No biologic basis for the findings was offered, but an immunologic mechanism was most prominently suspected. 
  • TRALI (transfusion-associated acute lung injury), that has been clearly associated with transfusion of blood from previously pregnant women and for which we have preventive measures in place, is not the explanation, since the effect appeared to operate months out from transfusion. 
  • In light of both contradictory and supportive previously published studies, the Dutch investigators called the work “very tentative” and for more work to “replicate these findings, determine their clinical significance, and identify the underlying mechanism.” 
  • Editorialists who critically reviewed the study agreed and stated as well that “(I)n light of the limitations of the study by Caram-Deelder et al, current criteria for blood donor selection should not change. However, additional investigation is needed.” 
  • The effect was statistically modest, but must be followed up with definitive research to understand if this effect is real or spurious. 
  • In the absence of a clearly plausible biological mechanism, transfusion remains one of the safest medical procedures in wide use, and patients should not be unduly concerned if their health care provider recommends an appropriate blood transfusion. 
  • Blood donor and recipient safety and maintaining a safe and available blood supply continues to be our highest priority.
1 For example, beyond being retrospective, no causes of death were enumerated to allow any assessment of either the plausibility of the association or mechanisms. Statistical adjustment for multiple comparisons were not made. Multivariate analyses to control for potentially relevant confounders was not described. Missing data on pregnancy status was noted by the authors. The findings became less consistent as the cohorts were broadened to include recipients of mixed gender components (likely including sicker patients and a more “real world” analysis). The age dependence of the effect measured, with younger males more affected, is unexplained.


Caram-Deelder C, Kreuger AL, Evers D et al. Association of blood transfusion from female donors with and without a history of pregnancy with mortality among male and female transfusion recipients. JAMA. 2017. 318:1471-78.

Cable RG, Edgren G. Blood transfusions from previously pregnant women and mortality interpreting the evidence. JAMA. 2017. 318:1445-8.

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