P-714 Prevalence of chromosomal abnormalities in oocyte donor candidates: a French survey of over 8200 karyotypes
Authors: Puy V , Bennani Smires B , Siffroi J  P , Tachdjian G , Pipiras E , Eustache F ,   T. F. N. G. B. G. The French National Gamete Banking Group
Published: July 2024

Abstract

Study question
Is karyotyping worth considering for fertile and childless oocyte donor candidates?

Summary answer
Karyotyping reduces the genetic risk of utilizing oocytes with balanced structural chromosomal rearrangements for recipient couples.

What is known already
While some countries including France consistently advocate for karyotype to be routinely performed, others suggest it as optional, specifically advising it for donors with a medical history indicating chromosomal rearrangements. Ravel et al. have demonstrated a higher incidence of balanced structural chromosomal rearrangements among 1196 french fertile oocyte donor candidates (FODC) compared to unselected newborns, raising the question whether oocyte donor recruitment could be biased towards chromosomally at-risk women. In 2016, France authorized childless oocyte donor candidates (CODC) to enhance recruitment, yet as of now, there is no reported study on their genetic status.

Study design, size, duration
A retrospective observational multicentric study conducted from January 2005 to October 2021.

Participants/materials, setting, methods
ODC were recruited within the French CECOS (Centre d’Etude et de Conservation des Œufs et du Sperme humain) network. Both FODC and CODC were compared to a control group composed of female newborns from literature. Quantitative and qualitative data were expressed as the median [25%–75%] or n (‰), respectively. Non-parametric Mann-Whitney tests were employed for quantitative parameters, while Chi-square tests or Fisher’s exact tests were used, as appropriate, to compare frequencies between groups.

Main results and the role of chance
A total of 8229 ODC from 22 CECOS centers were included in this study. FODC (n = 6339) and CODC (n = 1890) were compared to 8102 control female newborns. In total, 65 chromosomal abnormalities (7.9‰) were identified, leading to the exclusion of the ODC. This outcome was comparable to the 53 abnormalities observed in the control group (6.54‰, p = 0.3059). The occurrence of balanced structural chromosomal rearrangements was increased in ODC population (4.8‰) compared to controls (2.34‰, p = 0.0086). The occurance of reciprocal translocations was increased 5-fold in CODC (3.70‰) compared to the control group (0.74‰, p = 0.013). The number of gonosomal mosaics was notably increased in FOCD, with 17 cases (2.68‰) compared to the control group with six cases (0.74‰, p = 0.0052). Among chromosomal aberration carriers only two childless women (one reciprocal translocation and one gonosomal mosaïc) had fertility issues in their medical history with a diagnosis of premature ovarian failure.

Limitations, reasons for caution
This retrospective study was designed to examine ODC within the framework of French bioethics laws. ODC should adhered to specific criteria: being volunteers, anonymous, aged 18 to 38, and without any financial compensation. Since 2016, donors were permitted to retain around 50% of their gametes for personal oocyte cryopreservation.

Wider implications of the findings
Karyotyping is a straightforward and cost-effective approach to identify structurally balanced chromosomal abnormalities. Thus, chromosomal analysis limits genetic risks whithout resorting to the ethically debated expanded genetic screening in the ODC population. Nevertheless, it is crucial to communicate to gamete recipients the inherent genetic risks associated with any conception.

Trial registration number
not applicable