Six years experience in ovum donation using vitrified oocytes Report of cumulative outcomes impact of storage time and development of a predictive model for oocyte survival rate

Oocyte banking is clinically efficient. Estimation of the likelihood of having a child is provided. There is no way of estimating donors’ oocytes survival when considering baseline characteristics, storage time, or controlled ovarian stimulation parameters.

Ana Cobo, Ph.D., Nicolás Garrido, Ph.D., M.Sc., Antonio Pellicer, M.D., José Remohí, M.D.

Volume 104, Issue 6, Pages 1426-1434


To describe the clinical outcomes achieved after 6 years’ experience in ovum donation conducted with vitrified oocytes to attempt to find predictors of survival; and to provide information about the probability of having a baby according to the number of oocytes consumed.

Retrospective, observational study.

Private university-affiliated in vitro fertilization center.

Recipients of vitrified oocytes (January 2007–March 2013), including all the warming procedures (n = 3,610) and all the donations made during the same period (n = 3,467).


Main Outcome Measure(s):
Survival rate per warming procedure, cumulative delivery rates (CDR) per single donation cycle, oocyte-to-baby rate, and cumulative live birth rate (CLBR) per oocyte consumed.

Oocyte survival rate was 90.4%. It was not possible to develop a predictive model for survival owing to the lack of prognostic value of the studied variables. Implantation, clinical, and ongoing pregnancy rates per donation cycle were 39.0% (95% confidence interval [CI], 37.8–40.5), 48.4% (95% CI, 46.7–50.1), and 39.9% (95% CI, 38.3–41.5), respectively. Statistical differences were found when comparing blastocysts versus day 3 ETs (42.5%; 95% CI, 40.4–45.2 vs. 37.5%; 95% CI, 35.3–39.7 ongoing pregnancy rate). The CDR/donation cycle, including cryotransfers, was 78.8% (95% CI, 73.5–84.1). The oocyte-to-baby rate was 6.5%. CLBR increased progressively according to the number of oocytes consumed.

We provide detailed information about the high efficiency of using vitrified/warmed oocytes. There is currently no way of estimating donors’ oocytes survival when considering baseline characteristics, storage time, or controlled ovarian syndrome parameters. The probability of achieving a baby using vitrified oocytes increases progressively with the number of oocytes consumed.

  • Mario Gilberto Vega, MD

    Dear Dr. Cobo,

    Thank you for a very interesting article. Your delivery rate/donation cycle of 39.1% is similar to rates that are been seen in some centers in the United States using commercial egg banks. I have a clinical question: In the US it seems that we are very focused on adjusting estradiol doses to achieve E2 levels >200 and a thick endometrial lining, but in your protocol it seems you only check E2 levels and Endometrial Thickness once, do you change your protocol if there is not an adequate response? Also, when choosing route of administration, is there a reason why you use Oral Estradiol as opposed to Intramuscular or Vaginal?

    Thank you,

    • Ana Cobo

      Dear Dr Vega,
      Thank you for your interest in our work.
      When the response is not adequate we increase in 2mg the dose of oral E2 (8mg total dose). Only ocasionally when the endometrial lining is not improved we switch to the administration via vaginal (8mg). Also in rare cases with liver disease, our choice is the E2 patch.

  • Daniel J. Kaser, MD

    Dear Dr. Cobo and colleagues,

    Congratulations on this large report (n=42,000 oocytes) of oocyte cryosurvival, cumulative live birth rate per donation and oocyte-to-baby rate. The data your group presents is very reassuring, and contains some important figures for patient counseling: 90.4% oocyte survival following warming, 1.4% of cycles with no oocytes surviving, 6.5% oocyte-to-baby rate and a cumulative live birth rate per donation of 78.8%. Table 3 is also helpful, comparing live birth rates per oocyte consumed in the donor and autologous populations, according to age.

    Two clinical questions:
    1) In light of these impressive rates, has IVI moved to using only vitrified donor oocytes, or are fresh donor cycles still used. If so, could you please comment on how patients are counseled for one vs. the other?
    2) Does your center have an age cut-off for elective oocyte cryopreservation?

    Thanks very much for your comments.

    • Ana Cobo

      Dear Dr. Kaser,

      Thank you for your comments on our report.

      1) We have not yet switch to only egg-banking,
      basically for two reasons: 1) In our country fresh donation
      it is still allowed by law, 2)To proceed with whether a fresh or vitrified donation, sometimes it depends on the availability of oocytes/donors according to the recipients at any given moment. For example, let’s say we have some oocytes from the bank, already assigned
      to a recipient. However, the same day of thawing/donation, we have an OPU from another compatible donor (sometimes the same donor). In these cases, we may avoid thawing, and proceed with the fresh donation because we can offer the recipients the same chances with the fresh or the vitrified donation.
      Currently, the proportion is around 60% egg-banking and 40% fresh donations.

      2) We really don’t have any cut-off for elective cryopreservation but we prefer and counsel to do it at young age. We have analyzed our success rates in an elective fertility preservation population (Coming soon in FS) and have found strong differences with better outcomes in women ≤36y. Nevertheless, some pregnancies and live birth could be achieved in patients <36y or even in older than 40y. That is why we cannot say their chance is 0%. In these cases, we analyze every case individually, and counsel them clearly explaining the very low probability of success. In many cases, they still insist on going ahead with their purpose. In our upcoming manuscript, you will find very useful information on this regard.

      • Daniel J. Kaser, MD

        Great, thanks very much for the additional comments, Dr. Cobo. I look forward to the follow-up report about the IVI experience with elective oocyte cryopreservation as a function of age!

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