As of June 2023, the national registry of voluntary bone marrow donors was composed of 35% men and 65% women. A gap observed for many years, according to the biomedicine agency, which manages this registry.

"We do not know at all why there is such a difference but we observe it and it poses a problem for us, because transplant centers are oriented towards male donors in more than 70% of cases," said Dr. Catherine Faucher, director of hematopoietic stem cell sampling and transplantation (HSC) at the agency.

Doctors report that a transplant performed from a sample of bone marrow cells taken from a man significantly optimizes the chances of success.

This distinction is explained at the immunological level: in women, antibodies are developed naturally during each pregnancy (even if it is not carried to term). However, these antibodies complicate the good tolerance of the bone marrow graft after the transplant for the patient.

Since they are absent in men, the risk of complications is reduced.

When they have the choice between two compatible grafts, "transplant centers will therefore systematically favor a male donor," says Dr. Faucher.

Altruistic behaviours

If no study provides information on the motivations or questions of donors, the agency notes in the field that men question themselves more than women about the methods of collection.

This is why it is necessary to do pedagogy and "remember that in 80% of cases, it is a blood sample," she says. The sampling by puncture in the posterior bones of the pelvis, an intervention that is then done under general anesthesia, is performed in only 20% of cases.

For the first time this year, the biomedicine agency has launched a communication campaign exclusively targeting men aged 18 to 35, culminating in World Bone Marrow Donation Day on Saturday.

According to the French Blood Establishment (EFS) in 2022, 46.5% of donors were men against 53.5% of women © GEORGES GOBET / AFP/Archives

To a lesser extent, blood donation also illustrates a difference between men and women: according to the French Blood Establishment (EFS) in 2022, 46.5% of donors were men compared to 53.5% of women. However, men's donations represent 52% of the total, the latter being able to donate their red blood cell concentrates up to 6 times a year against 4 times for women.

Studies published by several teams of different nationalities converge on certain explanations, according to the EFS, including altruistic behaviors valued in women from an early age.

Double the number of donors

The typology of another type of donation, not interchangeable, is telling: that of gametes. In 2022, 990 women were candidates to donate their eggs, while 764 men donated their sperm.

These figures, which are rising, remain insufficient in the face of growing needs, especially in spermatozoa, explains the biomedicine agency.

For two years in France, the demand for ART with sperm donation has increased by 7.5 © MORTEN THUN / SCANPIX DENMARK / AFP / Archives

Indeed, in 2021 the bioethics law evolved to allow access to medically assisted procreation to single women and female couples. As a result, "for two years, the demand for assisted reproduction with sperm donation has been multiplied by 7.5," Marine Jeantet, director general of the biomedicine agency, told AFP.

For the past year, donors of gametes (spermatozoa and oocytes) have had to consent to children being able to request access to their identity and non-identifying data about them when they reach the age of majority.

A decree published this summer set March 31, 2025 as the deadline for the use of the stock of straws (gamete preservation tubes) constituted when consent to the lifting of anonymity was not mandatory.

"It is not yet known whether this lifting of anonymity will be a brake for men donating their sperm. But even if it is not, we will have to double the number of donors to meet the needs, "warns Ms. Jeantet.

© 2023 AFP