Literature
Clinical Pearls & Morning Reports
Published October 25, 2017
Of all the available means of fertility preservation, oocyte cryopreservation by means of vitrification (very rapid freezing) provides the highest yield, not only for women with benign diseases or those seeking fertility preservation for personal reasons but also for women with cancer. Ovarian-tissue cryopreservation is specifically indicated for adolescents and women in whom cancer treatment cannot be postponed. Read the latest Review Article.
Clinical Pearls
Q: What nononcologic conditions may be associated with premature ovarian insufficiency?
A: Fertility preservation should be offered to women with certain benign conditions that carry the risk of premature ovarian insufficiency. Many autoimmune and hematologic conditions sometimes require chemotherapy, radiotherapy, or both and sometimes even bone marrow transplantation. Other conditions can also impair future fertility, such as the presence of bilateral ovarian tumors, severe or recurrent ovarian endometriosis, and recurrent ovarian torsion.
Q:What is the preferred method for oocyte cryopreservation?
A:Data from a recent review suggest that the strategy of oocyte vitrification and warming is superior to slow freezing and thawing in terms of clinical outcomes. On the basis of this evidence, laboratories that continue to use slow freezing should consider transitioning to vitrification techniques for purposes of cryopreservation.
Morning Report Questions
Q: How important is the age of the patient when oocyte vitrification is undertaken?
A: Cobo et al. recently reported outcomes for 137 women who had undergone fertility preservation by means of oocyte vitrification for nononcologic reasons and subsequently returned to use their oocytes. A total of 120 women had undergone the procedure to circumvent age-related fertility decline. Among women who were 35 years of age or younger at the time of oocyte vitrification, the cumulative live-birth rate was much lower when only 5 oocytes were used (15.4%) than when 8 or 10 oocytes were used (40.8% and 60.5%, respectively). Among women who were older than 35 years of age at the time of the procedure, the cumulative live-birth rates were 5.1%, 19.9%, and 29.7% with 5, 8, and 10 oocytes, respectively. Hence, with 10 oocytes, the cumulative live-birth rate was twice as high in the group of women who were 35 years of age or younger (60.5%) as in the group of older women (29.7%).
Q: How is ovarian-tissue cryopreservation accomplished?
A: Ovarian tissue is removed in the form of multiple biopsy specimens (or an entire organ) and cut into cortical strips. The tissue is then cryopreserved by slow freezing on site (or transported to a processing site at a temperature of 4°C). After thawing, if there is no risk of transmitting malignant cells, the ovarian tissue can be grafted to the ovarian medulla (if at least one ovary is still present) or reimplanted inside a specially created peritoneal window. After reimplantation of ovarian tissue in the pelvic cavity, ovarian activity is restored in more than 95% of cases. The mean duration of ovarian function after reimplantation is 4 to 5 years, but the function can persist for up to 7 years, depending on the follicular density at the time of ovarian-tissue cryopreservation. The first pregnancy after this procedure was reported in 2004. The number of live births as of June 2017 exceeded 130. Transplanting ovarian tissue to heterotopic sites remains somewhat questionable, however, and only one pregnancy has been reported in a woman who underwent this procedure.
