P-413 Lessons learnt from a long-term fertility cryopreservation program regarding usage-rate of vitrified oocytes and embryos
Authors: Blais I , Koifman M , Aharoni A , Weiner-Megnazi Z , Younes G , Oron G , Lahav S 
Published: June 2023

Abstract

Study question
Does woman's age during cryopreservation affect usage-rate of the vitrified oocytes and embryos from fertility preservation cycles?

Summary answer
The usage-rate of vitrified oocytes and embryos from cryopreservation cycles is low. Sub-analysis shows a higher usage-rate with advanced age and increased storage time.

What is known already
previous studies show a 3-9% usage-rate in social oocyte freezing fertility preservation cycles. Studies show that social preservation of oocytes before the age of 39 is not cost effective. To the best of our knowledge, data is scarce regarding the vitrified oocyte and embryo usage-rate according to the woman's age during both social and medical fertility preservation cycles.

Study design, size, duration
A retrospective case series study including all fertility preservation cycles at our IVF unit between Dec 2010 and Jan 2023. During a period of 12 years, 558 cycles in 358 women without a known fertility problem were performed. Vitrification was performed in 535 cycles. A total of 3605 oocytes and 382 embryos were cryopreserved for social and medical reasons (272 and 286 cycles respectively).

Participants/materials, setting, methods
The treatment cycles were divided into 3 groups according to the time-period of cryopreservation, reflecting the length of storage. Group 1: 2010-2016 (54 cycles), Group 2: 2017-2020 (132 cycles), and Group 3: 2021-2023 (349 cycles). We analyzed usage-rate in each time group according to their age at freezing, 17-35 (334 cycles) or 36-44 (201 cycles)

Main results and the role of chance
Average age was 34±5 years (17-44). Overall, 30 women (30/358=8%) thawed their oocytes or embryos cryopreserved in 37 cycles (37/535=7%) of them 16 for social and 21 for medical reasons. In all three time-period groups there was a clear trend of increased usage among older women at cryopreservation (36-44y) compared to younger women (17-35y) : Group 1 [43%(9/21) vs 24%(8/33)], Group 2 [9%(6/64) vs 3%(2/68)] and Group 3 [8%(9/120) vs 1%(3/229)]; respectively. As shown, usage-rates also increased in accordance to length of storage. For thawed embryos positive β-hCG rate was higher for the 17-35 age group compared with 36-44 age groups [53% (10/19) vs 19% (3/16)] and Clinical pregnancy were [37% (7/19) vs 19% (3/16); respectively. For oocyte thawing usage-rates were extremely low; only one woman thawed her oocytes in the young age group and was pregnant and 6 women in the older age group thawed their oocytes and 2 were pregnant. Seven women transferred their frozen oocytes to another fertility center and the outcome is unknown. Overall usage-rate of vitrified oocytes and embryos from fertility preservation cycles is low. Sub analysis shows a higher usage-rate in correlation with women's age at time of cryopreservation and length of storage.

Limitations, reasons for caution
This is a single center retrospective study.

Wider implications of the findings
Cost effectiveness and success rates should be discussed with women undergoing fertility preservation cycles. Cost benefit should take into account the low usage rate, length of storage and the clinical pregnancy rates reported from oocyte and embryo thawing according to women's age.

Trial registration number
0029-23-CMC