[Precise identification of a cryptic balanced translocation in a couple with recurrent spontaneous abortions using...

Chromosome conformation-based karyotype analysis (C-MoKa) technology was used to test a couple who had experienced multiple adverse pregnancies in order to provide them with genetic counseling and reproductive guidance.

A couple presented at the Reproductive Medicine Center of the First Hospital of Lanzhou University in 2023 was selected as the study subject. Through C-MoKa testing, copy number variation sequencing (CNV-seq), and preimplantation genetic testing for aneuploidy (PGT-A), it was found that the couple's repeatedly miscarried fetuses and abnormal embryos exhibited highly similar chromosomal structural abnormalities. Using C-MoKa, the potential genetic abnormalities in both partners were traced, and reproductive guidance was provided based on the result. This study was approved by the Medical Ethics Committee of the Hospital (Ethics No.: LDYYSZLLKH2025-09).

CNV-seq analysis of the couple's miscarriage fetal chorionic villi showed del(18)(q21.2q23)(28.90 Mb) and dup(13)(q31.2q34)(26.26 Mb). Chromosomal karyotyping analysis of both partners showed no abnormality. From 2024 to 2025, the couple underwent three rounds of PGT-A assisted reproduction. The first embryo test showed del(13)(q31.2q34)(26.77 Mb) and dup(18)(q21.2q23)(29.08 Mb). The second embryo test showed dup(13)(q31.2q34)(26.26 Mb) and del(18)(q21.2q23)(28.90 Mb). And the third embryo test results showed complex chromosomal abnormalities. In 2025, after genetic counseling, the couple had opted C-MoKa test, which has detected no abnormality in the wife, but a balanced 46,XY,t(13;18)(q31.2;q21.2) translocation in the husband.

As a high-throughput sequencing method based on the three-dimensional conformation of chromatin, C-MoKa has the advantages of high resolution and high accuracy, and can accurately detect balanced translocations with similar banding patterns. It has therefore offered a powerful new tool for chromosomal analysis.