Preserving fertility consists of freezing or cryopreserving the male (sperm) and female (ovum) gametes, embryos or even germinal tissues (ovary or testicle), for future medically assisted procreation treatments.
Why fertility preservation?
Fertility preservation is recommended in different situations depending on the profile of each person.
Before a medical treatment
Medical treatments are the most common reason for fertility preservation. Some treatments or surgical interventions can have short or long-term consequences on human fertility, potentially causing a decrease or even a complete stop in the production of gametes. For example, patients needing chemotherapy or radiation therapy for cancer. In these specific cases, the freezing of reproductive material will take place before sterilizing treatments begin.
For social reason
In this particular case, the freezing of eggs or sperm is carried out preventively for non-medical reasons. For example, a difficulty in finding a life partner or a professional career are reasons more and more women resort to the freezing of their ova. This demand for gamete preservation mainly affects women, since from the age of 30, the quality and / or quantity of their eggs decreases gradually and even more rapidly after 36 years.
Conversely, although a man can produce sperm until the end of his life, studies show that the integrity of his sperm DNA increases with age, particularly from the age of 50. For men, semen freezing is recommended when the sperm parameters do not meet the WHO's recommendations. Some men may also decide to freeze their sperm as a preventive measure, when they are exposed to toxic substances at work. For instance, military people exposed to chemical weapons or farmers being exposed to pesticides should consider preserving their fertility.
During a gender transition
During a gender transition journey, hormonal and / or surgical treatments can have an impact on future fertility potential.
Preservation techniques: for women
Freezing of eggs
This procedure concerns pubescent women, that is, of women of childbearing age. After ovarian stimulation, it consists in collecting mature eggs (preferably) or even sometimes after in vitro maturation. These eggs are hence frozen by vitrification.
Back in the days, both eggs and embryos were preserved by a slow-freezing technique, with a survival rate of roughly 60%. The eggs' freezing has greatly improved since the development of a vitrification technique (year 2000) which improved egg's survival (90%) and the chances of pregnancy after in vitro fertilization.
Freezing of embryos
This method requires the collection of mature eggs. It usually requires ovarian stimulation. It also requires the involvement of the spouse or a donor, and the existence of a parental project.
After in vitro fertilization, the embryos produced are generally vitrified at the blastocyst stage (5 days of life). This procedure is therefore a preservation of the couple's fertility and not only of the woman, since the embryos can only be used within and with the agreement of both partners.
The purpose of this practice is to conserve the primordial ovarian follicles, at the level of the ovarian cortex.
It is the only technique possible in pre-pubescent and children but can also be offered in pubescent women. It requires no ovarian stimulation.
An entire ovary or biopsy fragments are taken. It is a heavier medical intervention since it requires surgery under general anesthesia.
When it's time to start a family, the tissues are thawed and grafted to the patient. This restores the endocrine function of the ovaries (production of sex hormones) and therefore leads to the resumption of the ovarian cycle. Ovarian tissue transplantation has already led to the birth of hundreds of children around the world.
Preservation techniques: for men
The freezing of sperm is normally done after sperm collection by masturbation. However, in the event of failure, alternative procedures such as cryptozoospermia, azoospermia or necrozoospermia can be used to try to recover sperm from the epididymis or testis.
If, despite everything, the operation is not successful, it is still possible, as an alternative, to freeze part of the testicular tissue. Freezing testicular tissue is, for the time being, the only freezing procedure possible in pre-pubertal children who do not produce sperm.