IVF Using Frozen Eggs Less Successful Than Fresh Ones
When fresh, instead of frozen, donor eggs are used, chances of a successful pregnancy and birth is higher,according to a new study.
Use of eggs, or oocytes, donated for in vitro fertilization (IVF) has grown in recent years. Traditionally, donated fresh oocytes have been used immediately, creating embryos for transfer into the uterus, with extra embryos being cryopreserved for later use.
“more widespread clinic-specific data on the safety and efficacy of oocyte cryopreservation … before universal donor oocyte banking can be recommended.”
Based on data that IVF outcomes with cryopreserved and fresh donor oocytes are comparable, some IVF centers established frozen donor egg banks. But data reflecting IVF outcomes in routine clinical practice with cryopreserved donor oocytes have not previously been published.
Fresh vs. Cryopreserved
Researchers from the Center for Human Reproduction, New York took data from the 2013 annual report of U.S. IVF center outcomes published by the Society for Assisted Reproductive Technology to compare live birth and cycle cancellation (started IVF cycles which do not reach egg retrieval and/or embryo transfer) rates using either fresh or cryopreserved donor oocytes.
The data set is based on center-specific voluntarily reported outcomes from 380 of 467 (81 percent) U.S. based fertility centers, which in 2013 collectively performed 92 percent of all IVF cycles.
Out of 11,148 egg donation cycles, 2,227 (20 percent) involved use of cryopreserved donor eggs. Initiated cycles were canceled in 12 percent of fresh oocyte cycles vs 8.5 percent of cryopreserved oocyte cycles.
Per started recipient cycle, the live birth rates were 50 percent with fresh vs 43 percent with cryopreserved oocytes. Per embryo transfer, the live birth rates were 56 percent with fresh vs 47 percent with cryopreserved oocytes.
Writing that the reasons for lower live birth rates with use of cryopreserved oocytes remain to be established, the authors note:
“One possible explanation is less opportunity for proper embryo selection due to smaller starting numbers of oocytes, leading to fewer embryos available for transfer. Alternatively, oocyte quality may be negatively affected by cryopreservation and thawing.”
They add that the added convenience and lower cycle costs with use of cryopreserved oocytes must be balanced against the lower live birth rates.