O-084 Outcomes of female fertility preservation with cryopreservation of oocytes or embryos: a population-based study
Authors: Ter Welle - Butalid E , Derhaag J , Vriens I , Goddijn M , Balkenende E , Beerendonk I , Bos A , Homminga I , Benneheij S , Van Os L , Smeenk J , Verhoeven M , Van Bavel C , Tjan-Heijnen V , Van Golde R 
Published: July 2024

Abstract

Study question
What are the reproductive outcomes observed of patients who cryopreserved oocytes or embryos in the context of fertility preservation in the Netherlands?

Summary answer
After 10 years follow-up, 25.5% of the women used their cryopreserved oocytes or embryos to attempt pregnancy and of these, 34.6% had a live birth.

What is known already
Fertility preservation through freezing oocytes or embryos is an established treatment for women with a risk of premature ovarian failure (caused by a benign or oncological disease) or physiological age-related fertility decline. Little is known about the success of freezing protocols, utilization rate of oocytes or embryos and live birth rates.

Study design, size, duration
A retrospective nationwide observational study was performed in the Netherlands. Data were collected between 2017-2019 from all women who cryopreserved oocytes or embryos more than two years ago in the context of fertility preservation in ten out of twelve IVF centers in the Netherlands.

Participants/materials, setting, methods
In total 1112 women were included in this study. Medical files and patient databases were used to extract data. The study protocol was approved by the medical ethics committee.

Main results and the role of chance
Fertility preservation cycles are performed increasingly over the years. In the first years (2004-2007) less than 10 cycles per year were performed, which increased to more than 300 cycles per year in ten years’ time (since 2016). Initially embryos were frozen in the context of fertility preservation. In the later years cryopreservation of oocytes became the standard approach. The median number of oocytes cryopreserved was 13 per woman (range 1-52) and of embryos cryopreserved was 6 (range 1-32). Cryopreservation of oocytes versus embryos resulted in a comparable median number of eligible embryos for transfer (3 and 4 embryos respectively). The 5-year utilization rate was 12.3% and 10-year utilization rate was 25.5%. The cumulative clinical pregnancy rate after embryo transfer of cryopreserved oocytes or embryos was 39.2% and the live birth rate was 34.6% per patient. The return rate of those who had fertility preservation due to benign diseases was higher than for the other indications after five years, namely 17.1% (p &lt; 0.05). After ten years the return rates for the other indications increased to similar percentages for all indications.

Limitations, reasons for caution
The follow-up period varied between patients and not all cryopreserved material was used yet at the end of this study. This might have led to underestimated pregnancy rates. Further, intention-to-treat analysis could not be performed since women who had a fertility preservation procedure without freezing were not included.

Wider implications of the findings
This study provides data on the reproductive outcomes after fertility preservation. This knowledge can be informative for professionals and future patients to improve counseling and informed decision making regarding ovarian stimulation in the context of fertility preservation.

Trial registration number
n/a