[Fertility preservation in prepubertal children].

Gonadotoxic therapies during childhood may impair future fertility in adult life and fertility preservation techniques should be discussed before starting gonadotoxic therapies. In both sexes, fertility preservation often means immature gametes cryopreservation. For girls, ovarian tissue cryopreservation is the only existing option to preserve fertility in prepubertal girls at risk of premature ovarian failure. This promising approach involves the storage of a large number of follicles, which could subsequently be transplanted or cultured to obtain mature oocytes. The results of ovarian tissue cryopreservation in adults are encouraging. At least nine children have been born after orthotopic reimplantation of frozen-thawed ovarian cortex. None of these pregnancies were obtained by reimplantation of ovarian tissue harvested before puberty; however, the probability of restoring fertility should be higher for younger girls, as their ovarian cortex clearly contains a large number of follicules. In vitro growth of primordial follicles to mature oocytes could be an option but this goal has not yet reached in humans. This option may be reach in the future, when young patients are in their twenties or thirties. For boys, spermatogonial stem cells can be cryopreserved and uni or bilateral testicular pieces can be stored for future use. Animal data reveals that healthy offspring were reported after grafting of frozen testicular cell suspensions or tissue pieces in different species. Although recent data show promising results, restoring fertility by using frozen testicular cells after transplantation or in vitro culture is not shown yet. Then, immature testicular tissue cryopreservation for prepubertal boys is still an experimental procedure. However, as their use for restoring fertility should not be requested before 10-30 years, a long time is given for advances in medical research.