The location of a translocation breakpoint, rather than fragment size, is associated with spermatogenic function

Male carriers of balanced reciprocal translocations can experience impaired spermatogenesis and adverse pregnancy outcomes. The impact of translocation fragment size and breakpoint location on these outcomes remains unclear.

To investigate whether the location and size of translocated fragments relate to spermatogenic function, embryo aneuploidy ratio, and pregnancy outcomes in couples with male chromosomal translocation.

In total, 103 couples with male reciprocal translocation were included and these couples underwent 116 pre-implantation genetic testing cycles. Patients were divided into Group A (at least one translocation segment size <10 Mb) and Group B (both segment sizes ≥10 Mb) to compare the association of translocation segment size on spermatogenic function, embryo aneuploidy ratio, and pregnancy outcomes. Additionally, patients were categorized into Group I (normal/mild-moderate oligospermia) and Group II (severe oligospermia) on the basis of sperm concentration, to compare the relationship of translocation breakpoint position on semen output.

No significant differences were found between Groups A and B in the proportion with severe oligozoospermia (26.47% vs 21.74%), euploid blastocyst rate (35.64% vs 36.18%), or cumulative pregnancy rate (42.11% vs 55.26%). However, the proportion of couples with 1q fragment was significantly higher in Group II than in Group I (16.28% vs 3.25%).

The size of male autosomal translocation fragments is not significantly associated with sperm concentration or pregnancy outcomes, although translocations involving the 1q fragment may relate to spermatogenic dysfunction.

Genetic counseling for male translocation carriers should prioritize breakpoint location, particularly on 1q, over fragment size when evaluating spermatogenic impairment risk.