Short Communication: Cryopreserved Sibling Oocytes and Intracytoplasmic Sperm Injection Rescue Unexpectedly Poor Fertilization in Conventional In Vitro Fertilization

Abstract

Purpose : To report a successful pregnancy from cryopreserved sibling oocytes and intracytoplasmic sperm injection (ICSI) for an infertile couple with an unexpectedly low fertilization rate in the fresh in vitro fertilization (IVF) cycle. Methods : The woman had bilateral tubal obstruction and polycystic ovarian syndrome. The man had normal semen parameters. The couple underwent a cycle of controlled ovarian hyperstimulation in that 20 oocytes were retrieved. Twelve oocytes were conventionally inseminated and eight were cryopreserved using a slow freezing method. However, only one oocyte was fertilized, and no pregnancy was achieved. In the next cycle, the frozen oocytes were thawed and ICSI was performed. Results : After thawing, seven oocytes (88%) survived and one was damaged. Six were at the metaphase II stage and were injected. Five (83%) achieved normal fertilization, and all of them cleaved (100%). After replacement of the embryos, a singleton pregnancy developed. A healthy female baby was delivered at term. Karyotyping revealed 46, XX. Conclusions : In addition to well-known indications, cryopreservation of excess sibling oocytes for patients receiving IVF has a possible advantage of preventing unexpectedly low fertilization rate or fertilization failures.

Impact of oocyte cryopreservation on embryo development

“…The results reported here are in agreement with previous data generated on a small number of cases (43,44) reporting on a slower cleavage rate in frozen cycles when compared with the sibling fresh oocytes. This behavior suggests that even if surviving thawing, the process of oocyte cryopreservation by slow freezing has a negative effect on the potential of further growth that is evident as early as the first cleavage divisions.…”

The Mare: A Pertinent Model for Human Assisted Reproductive Technologies?

“…Oocytes are more sensitive to freezing and thawing procedures and the use of vitrification has considerably improved the results (reviewed in [ 181 ]), allowing ART center to largely proposed oocyte cryopreservation in fertility preservation programs. Despite enormous progress made in vitrification techniques, oocytes remain the cells mostly exposed to damage in the freezing/thawing process when compared to embryos and spermatozoa [ 188 , 189 ]. For example, the volume to surface ratio of the oocyte is greater than other cells, thus complicating the dehydration process.…”