This could be avoided if, instead of using hormones to stimulate a person’s ovaries to release mature eggs, doctors would remove pieces of the ovaries themselves and somehow obtain mature eggs in the lab. This would involve taking immature eggs and coaxing them into developing, to the stage where they can be fertilized by sperm.
This has already been achieved in some cancer survivors. Some cancer treatments are toxic, especially to eggs and sperm. Adults are often advised to store healthy eggs or sperm before starting these treatments. But it is not an option for children who have not yet passed puberty.
However, if parts of the ovaries are removed from children, some clinics have been able to use this tissue to later generate mature eggs and fertilize them with sperm, implanting the resulting embryo back into those same people when they are adults. The technique seems to work and healthy babies are born. Last year, three US-based societies for reproductive medicine issued a statement concluding that the technique should no longer be considered experimental.
The technique has not yet been used to help transgender people have babies, but Christodoulaki and her colleagues believe it could. To find out, they tried the approach in ovaries donated by trans men.
The team started with ovaries donated by 14 transgender men aged between 18 and 24 who had their organs removed as part of gender-affirmation treatment. All participants underwent testosterone therapy for an average of 26 months, and some also took medication to prevent menstruation.
First, the team removed eggs that were days from being released from the ovaries. The team repeated the process with similar immature eggs donated by cisgender women. After 48 hours in the laboratory dish, the eggs appeared to be ready to be fertilized by sperm.
In both cases, about half of the immature eggs were successfully matured in the laboratory. But something seemed amiss when the team tried to fertilize the eggs with sperm. While 84% of cisgender women’s eggs were able to be fertilized, the figure was only around 45% for trans men.
By the time the embryos were five days old—the point at which they would normally be transferred to a person’s uterus—only 2% of those created from the eggs of trans men were still alive, compared to 25% of embryos from the eggs of cis women.