Chromosomal abnormalities in oocyte donor candidates: a French survey of over 8200 karyotypes.

Objective: To study karyotypes of more than 8,200 oocyte donor candidates in nulliparous or multiparous women compared to a reference population.

Design: A retrospective observational multicentric study.

Subjects: The study included two cohorts of oocyte donor candidates recruited between January 2005 and October 2021: multiparous women with at least one child at the time of recruitment, and nulliparous women. Both were compared to a reference population composed of female newborns from literature.

Exposure: Not applicable.

Main outcome measures: Blood lymphocyte karyotype.

Results: A total of 8229 oocyte donor candidates from 22 fertility centers were included in this study. Nulliparous women (n=1890) and multiparous ones (n=6339) were compared to 8102 female newborns. Overall, 65 candidates were carriers of chromosomal abnormalities and were therefore excluded from the donation process (0.79%, 95% CI: 0.60-0.98). The occurrence of balanced structural chromosomal rearrangements was globally increased in the study population (0.49%, 95% CI: 0.34-0.64) compared to female newborns (0.24%, 95% CI: 0.34-0.64, p=0.0086). The number of reciprocal translocations was increased 5-fold in nulliparous oocyte donor candidates (0.37%, 95% CI: 0.10-0.64, p=0.013). The incidence of sex chromosome mosaicism was notably increased in multiparous oocyte donor candidates, with 17 cases (0.27%, 95% CI: 0.14-0.40, p=0.0052). Among chromosomal aberration carriers only two nulliparous women (one reciprocal translocation and one sex chromosome mosaicism) had fertility issues with a diagnosis of premature ovarian failure.

Conclusion: In this comprehensive 16-years French experience of karyotyping in oocyte donor candidates, we confirmed an increased incidence of balanced structural chromosomal rearrangements, especially among those without children at the time of recruitment. Karyotyping could be considered to identify any chromosomal abnormalities that may not be easily detectable through medical questioning. These abnormalities pose an inherent genetic risk for gamete recipients if left undetected.