In Vitro Fertilisation Using Frozen Oocytes Associated With Lower Live Birth Rates
CHICAGO -- August 11, 2015 -- Compared to using fresh oocytes for in vitro fertilisation (IVF), use of cryopreserved donor oocytes in 2013 was associated with lower live birth rates, according to a study published in the August 11 issue of JAMA.
Use of oocytes donated for in IVF has increased in recent years. Donated fresh oocytes traditionally have been used immediately, creating embryos for transfer into the uterus, with extra embryos being cryopreserved for later use. In January 2013, the American Society for Reproductive Medicine declared the technique of oocyte cryopreservation no longer experimental, although it called for 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 centres established frozen donor egg banks. However, data reflecting IVF outcomes in routine clinical practice with cryopreserved donor oocytes have not previously been published.
Vitaly A. Kushnir, MD, Center for Human Reproduction, New York, New York, and colleagues used data from the 2013 annual report of US IVF centre outcomes published by the Society for Assisted Reproductive Technology to compare live birth and cycle cancellation rates using either fresh or cryopreserved donor oocytes. This data set is based on centre-specific voluntarily reported outcomes from 380 of 467 fertility centres in the United States, which in 2013 collectively performed 92% of all IVF cycles.
Of 11,148 oocyte donation cycles, 2,227 (20%) involved use of cryopreserved donor oocytes. Initiated cycles were cancelled in 12% of fresh oocyte cycles versus 8.5% of cryopreserved oocyte cycles. Per started recipient cycle, the live birth rates were 50% with fresh versus 43% with cryopreserved oocytes. Per embryo transfer, the live birth rates were 56% with fresh versus 47% with cryopreserved oocytes.
The reasons for lower live birth rates with use of cryopreserved oocytes remain to be established.
“One possible explanation is less opportunity for proper embryo selection due to smaller starting numbers of oocytes, leading to fewer embryos available for transfer,” the authors wrote. “Alternatively, oocyte quality may be negatively affected by cryopreservation and thawing.”
They also noted that the added convenience and lower cycle costs with use of cryopreserved oocytes must be balanced against the lower live birth rates.
The authors pointed out that these findings need to be viewed with caution because they are based on anonymised aggregate outcomes, which do not allow adjustments for confounding patient characteristics, such as donor and recipient ages, infertility diagnosis, and embryo stage.
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