There seems to be an increased risk of dying when men receive blood from women who have previously been pregnant. The researchers still do not know why.

A Dutch study that involved more than 30,000 patients who received nearly 60,000 blood transfusions showed different risks of death depending on who had donated the blood. If men received blood from women who had been pregnant, the risk of death increased.

If the blood came from women who had been pregnant, it resulted in 101 deaths of 1,000 recipients per year. If the blood came from men, it was associated with 80 deaths per 1,000 recipients per year. If the blood came from women who had never been pregnant, there was no such difference from blood that came from men.

“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”

– Dr. Rutger Middleburg wrote in the Journal of the American Medical Association.

Antibodies are created in pregnant women that aim to protect the fetus and the researchers hypothesize that these could pose a possible cause.

“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.”

“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.”

“Further research is needed to replicate these findings, determine their clinical significance, and identify the underlying mechanism.”

– Rutger Middleburg

Nevertheless, this apparent factor should affect future medical routines, to mitigate the mortality risk by avoiding giving blood from once pregnant women to men, when possible.


Camila Caram-Deelder et al. “Association of Blood Transfusion From Female Donors With and Without a History of Pregnancy With Mortality Among Male and Female Transfusion Recipients” Oct 17, 2017, JAMA. 2017; 318 (15): 1471-1478. Doi: 10.1001 / jama.2017.14825