A landmark study of blood transfusions has revealed a startling link between the blood of pregnant donors and the impact on male recipients.
For the study, scientists examined the death rates of 31,118 patients who received 59,320 red blood cell transfusions at hospitals in The Netherlands from 2005-15, the Telegraph reports.
Researchers found that men studied under the age of 50 were 1.5 times more likely to die within three years if they had received a red blood cell transfusion from a female donor who had ever been pregnant. By comparison, women who received transfusions did not seem to have an elevated risk, Scientific American reports.
The study was published in the Journal of the American Medical Association.
Dr Rutger Middelburg, from Sanquin Research in Leiden explained: “Male recipients who received a transfusion from an ever-pregnant female donor had a statistically significant increase in mortality compared with those who received a transfusion from a male donor or from a female donor without a history of pregnancy.”
Transfusion-related acute lung injury (Trali) was the most common cause of death. Researchers theorised that women who had fallen pregnant acquire antibodies to protect their baby, which then may trigger a reaction in men that could be fatal.
“The association of increased mortality among male patients who received transfusions from ever-pregnant donors suggests a possible mechanism based on immunologic changes occurring during pregnancy,” Dr Rutger Middelburg wrote in the medical journal.
“An alternative explanation could be a difference in iron status between ever-pregnant female and male donors. Some studies also report differences in red blood cell physiology between the sexes.”
However, the research team emphasised the need for additional research to test their findings.
“Further research is needed to replicate these findings, determine their clinical significance, and identify the underlying mechanism,” Dr Rutger said.
According to the Scientific American, the American Red Cross have also declared the study is not conclusive enough to alter how red blood cell donors are currently matched.
Gustaf Edgren, an epidemiology associate professor and haematologist made the point that his own research suggests the sex of a donor does not make a difference to the donor.
“Our data is really not compatible with this finding,” he explained.