Outcomes of Fresh and Cryopreserved Oocyte Donation

Use of oocytes donated for in vitro fertilization (IVF) has increased in recent years.¹ 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 (egg freezing) 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.”²

Based on data that IVF outcomes with cryopreserved and fresh donor oocytes are comparable,³ some IVF centers established frozen donor egg banks. However, data reflecting IVF outcomes in routine clinical practice with cryopreserved donor oocytes have not been published.

We used data from the 2013 annual report of US IVF center outcomes published by the Society for Assisted Reproductive Technology⁴ to compare live birth and cycle cancellation rates using either fresh or cryopreserved donor oocytes. This aggregate data set is based on center-specific voluntarily reported outcomes from 380 of 467 (81.4%) US-based fertility centers, which in 2013 collectively performed 91.7% of all IVF cycles. Once verified, data are transmitted to the US Centers for Disease Control and Prevention in accordance with legal requirements.⁵

Annual validation via select onsite visits, including chart review, suggests low-discrepancy rates (<5%) for reported data,⁶ which are publicly available online.⁴ Because individual patients cannot be identified, the study received expedited institutional review board approval and a waiver of the need for informed consent. Cycles involving cryopreserved embryos were excluded.

Canceled cycles and live births per recipient IVF cycle start and per embryo transfer procedure were compared using the 2-tailed Fisher exact test and the Wilson test for binomial proportions. The number of embryos transferred was compared using a 2-sided Wald test and a P value for Poisson distribution. A 2-sided P value of <.05 was considered statistically significant. All statistical analyses were performed using SAS version 9.4 (SAS Institute Inc).

Of 11 148 oocyte donation cycles, 2227 (20.0%) involved use of cryopreserved donor oocytes (Table). Initiated cycles were canceled in 11.7% of fresh oocyte cycles vs 8.5% of cryopreserved oocyte cycles (difference, 3.2% [95% CI, 1.9%-4.6%]; P < .001). Per started recipient cycle, the live birth rates were 49.6% with fresh vs 43.2% with cryopreserved oocytes (difference, 6.4% [95% CI, 4.1%-8.7%]; P < .001). Per embryo transfer, the live birth rates were 56.1% with fresh vs 47.1% with cryopreserved oocytes (difference, 9.0% [95% CI, 6.6%-11.4%]; P < .001). Patients using fresh oocytes had a mean of 1.7 embryos transferred vs 1.6 embryos for patients using cryopreserved oocytes (difference, 0.1 [95% CI, 0-0.2]; P = .001).

In 2013, 20.0% of all studied donor egg recipient cycles used cryopreserved oocytes. In vitro fertilization using cryopreserved donor oocytes was associated with lower cancellation rates, but also lower live birth rates than donor cycles using fresh oocytes.

Availability of cryopreserved oocytes simplifies IVF logistics because coordination with the donor’s cycle is no longer necessary. Banked oocytes also may reduce costs per IVF cycle because oocytes from one donor can be shared by several recipients. However, the added convenience and lower cycle costs must be balanced against the lower live birth rates with use of 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. Alternatively, oocyte quality may be negatively affected by cryopreservation and thawing.

These findings need to be viewed with caution because they are based on anonymized aggregate outcomes, which do not allow adjustments for confounding patient characteristics, such as donor and recipient ages, infertility diagnosis, and embryo stage. Another limitation is inability to account for clustering of cycles within patients because data are reported per cycle rather than per patient. Therefore, even though these data offer new information about use of cryopreserved oocytes in donation cycles, they also demonstrate the need for additional studies.

Corresponding Author: Vitaly A. Kushnir, MD, Center for Human Reproduction, 21 E 69th St, New York, NY 10021 (vkushnir@thechr.com).

Author Contributions: Dr Kushnir had full access to all of the data in the study and takes responsibility for the integrity of the data and the accuracy of the data analysis.

Study concept and design: Kushnir, Barad.

Acquisition, analysis, or interpretation of data: All authors.

Drafting of the manuscript: Kushnir.

Critical revision of the manuscript for important intellectual content: All authors.

Statistical analysis: Kushnir, Darmon.

Administrative, technical, or material support: Barad, Gleicher.

Study supervision: Gleicher.

Conflict of Interest Disclosures: The authors have completed and submitted the ICMJE Form for Disclosure of Potential Conflicts of Interest. Dr Kushnir reported serving as a consultant to the US Centers for Disease Control and Prevention (CDC). Drs Kushnir, Barad, and Gleicher reported being co-owners of a number of already awarded and still pending US patents; however, none are related to the topic of this article. Drs Barad and Gleicher reported receiving patent royalties from Fertility Nutraceuticals LLC. Dr Gleicher reported being a shareholder in Fertility Nutraceuticals LLC and owner of the Center for Human Reproduction (CHR). The CHR routinely reports in vitro fertilization outcome data annually to the CDC and the Society for Assisted Reproductive Technology. No other disclosures were reported.