Lessons Learned From A 10 Years Cryoembryo Vitrification Program: The Age Of The Oocyte Matters.

Embryo vitrification has been a breakthrough in assisted reproduction (ART), allowing higher cost-effectiveness of ART cycles by offering a higher number of embryos to be transferred per cycle, given the high survival rate of these embryos. The best-Known prognostic factor for success in fresh ART cycles is the oocyte's age (OA). Our objective is to analyze the influence of OA in the outcome of cryotransferences (CTs) conducted with vitrified embryos. Retrospective cohort study in a university- affiliated infertility center. Ongoing pregnancy rate (OPR) and live birth rate from n= 9246 women undergoing 14442 CTs from January 2007 and December 2017 (6199 from egg donation, 8243 from own oocytes) involving 22263 Emb vitrified, was analyzed depending on the OA. χ2 test was used for pregnancy rates comparisons. A logistic regression was performed with live birth rate as the response variable and the OA, adjusting for patient age and BMI as well as for the type of CTs, and special analysis was performed considering only OA less than 36 and considering the origin of the eggs. Data are presented as means or proportions (95% confidence intervals). Total mean OA the day of fertilization of the embryos was 30.78 y ( 30.69-30.87 ), from donated CTs OA was 25,90 (25.79-26.01), own oocytes CTs OA 34,45 ( 34.37-34.52), and mean receiver’s age 38.03 y, embryo survival 97,29 %(97.13-97.46 ), 1.84 embryos warmed ( 1.81-1.85), 1.54 embryos transferred ( 1.53-1.55). Biochemical pregnancies, clinical pregnancy, and OPR/warming cycle were 54,29 %(53.47-55.10), 44.55%(43.74-45.37), and 35.09 %(34.31-35.88). According to the model, for each year-increase in the OA, the odds of achieving a live birth rate (LBR) decrease by 1.83 % (OR 0.981.95 % CI 0.97-0.99, p< 0.001). In the younger group (until OA 35 y), the change from donated to own oocytes was found to have a statistically significant effect (OR 0.85 CI 95 %; 0.78-0.06, p=0-01), diminishing the odds of having an OPR by 14%. OA is a key prognostic factor in the outcome of vitrification CTs program. OA yields a clear annual negative impact on OPR. In younger OA group, the fact that they come from egg donors and not from own oocytes equally affects the results. Increasing the number of embryos transferred should be taken in consideration for elder women according to these data.