O-038 Is a 10-year retention period sufficient after elective oocyte vitrification (EOV)?
Authors: Nekkebroeck J , Leunens L , Buyse E , Cooreman R , Tournaye H , De Vos M 
Published: June 2023

Abstract

Study question
In Belgium, by law, a retention period of 10-years is standard. Is this period sufficient for women to return to the clinic and use their vitrified oocytes?

Summary answer
A standard cryopreservation period of 10-years seems sufficient since half of the women returned to the fertility clinic and 96% used the vitrified oocytes.

What is known already
The main driver for elective oocyte cryopreservation is to buy more time to find a suitable partner. The question remains whether 10 years of cryopreservation is sufficient for women to accomplish their goal of finding a partner and procreate with or without using their vitrified oocytes. The return rates and the utilisation rates of the vitrified oocytes reported in the literature are low. Most women do not use their vitrified oocytes. Little is known about women's reproductive pathways after EOV and the destination of the expired surplus vitrified oocytes.

Study design, size, duration
Computerized clinical data were retrieved from a pioneer cohort of women who underwent EOV in our centre for age-related reasons more than 10 years ago (between 2009 and 2012). Hence, the legal cryopreservation period of their oocytes expired between 2019 and 2022. We documented reproductive choices for those who returned to the centre and we investigated the intended destination of the expired vitrified oocytes for those who did not return.

Participants/materials, setting, methods
Data were collected from clinical charts of women who vitrified oocytes. According to Belgian law, unused vitrified oocytes expire when reaching the age limit of 48 years for use or by reaching the standard cryopreservation period of 10 years. We evaluated whether women eventually started treatment, assessed their relational status, the utilisation rate of the vitrified oocytes and the intended destination of the vitrified oocytes as stated in their informed consents.

Main results and the role of chance
117 women vitrified their oocytes at least 10 years ago. Women's oocyte cryopreservation period expired because they were either beyond the age limit for use (n = 82) or because the legal oocyte cryopreservation period of 10 years was reached (n = 35). Five women requested transport of their oocytes for treatment in a centre abroad.
Fifty-two out of 117 women (44.4%) returned for assisted reproduction. Eventually, 96% (50/52) of them used their vitrified oocytes for treatment and 21/50 had a child or ongoing pregnancy. Upon return to the clinic, 22 women were single and 27 had found a partner, two women returned with a co-parent and one woman had a female partner. Furthermore, 7/117 women returned to the clinic but eventually refrained from treatment.
Fifty-one women never returned to the centre. Only five women asked to prolong the cryopreservation period for medical reasons. The others not using their vitrified oocytes, did not initiate further action concerning the cryopreservation period, use or destination of their stored oocytes. Hence, the destination of the cryopreserved oocytes was according to the women's choice stated in the informed consent. The majority donated their oocytes for research (60%), others (31%) opted to destroy the oocytes after 10 years of cryopreservation.

Limitations, reasons for caution
It was not possible to map out the reproductive pathway of women who did not return to the centre and whose vitrified oocytes expired for use. Follow-up of reproductive choices and outcomes in women who did not return for treatment is required for a comprehensive appraisal of EOV.

Wider implications of the findings
The vast majority of the women who returned for treatment used their vitrified oocytes. Those not returning did not initiate further action concerning the use or destination of their vitrified oocytes. These results add to our knowledge on the utilisation rate after EOV, essential to improve counselling of future EOV-candidates.

Trial registration number
not applicable