Study finds pregnant women's blood can be deadly to men

The research has sparked the mother of all medical conundrums with speculation immunologic changes during pregnancy might explain the phenomenon. Photo / Getty Images

An alarming Dutch study has found men who have a blood transfusion are 1.3 times more likely to die if the blood comes from a woman who has been pregnant at some stage.

Nearly 60,000 blood transfusions in six major Dutch hospitals were studied in the research published in the Journal American Medical Association.

There were 101 deaths per 1,000 person years among men who received blood from a woman who had been pregnant at some stage in her life.

This compared to the 80 deaths per 1,000 person years when the blood donor was male.

Men who received blood from a never pregnant woman had a mortality rate of 78 per 1,000 person years versus 80 deaths when the blood came from a man.

The research has sparked the mother of all medical conundrums with speculation immunologic changes during pregnancy might explain the phenomenon.

Other theories include that there could be a difference in iron status between ever-pregnant female and male donors.

Iron deficiency in donors has recently been shown to be associated with worse recovery of red blood cells after transfusion.

"Further research is needed to replicate these findings, determine their clinical significance, and identify the underlying mechanism," the authors write.

A spokesman for Australia's Red Cross said it had no plans to change its practices in the wake of the research.

"The research at this stage is very preliminary, and the study authors acknowledge it has limitations," the spokesman said.

The data would need to be verified by further studies before the Red Cross altered its policies, he said.

If clinicians had concerns about using blood from once pregnant women in transfusions they could contact the Red Cross, the spokesman said.

According to the New Zealand Blood Service website, criteria for pregnant women to donate blood includes a deferral period which "should last as many months as the duration of the pregnancy."

It also advises against donating blood while breast-feeding: "Following childbirth, the deferral period is at least 9 months (as for pregnancy) and until 3 months after your baby is significantly weaned."