Chromosomal segregation in sperm of the Robertsonian translocation (21;22) carrier and its impact on IVF outcome.

Abstract

To assess the variability of meiotic segregation patterns in sperm of Robertsonian translocation (RobT) carrier t(21;22) and present effect on reproductive outcome. Infertile couple enrolled in IVF/ICSI program. Sperm chromosomal segregation analysis was done using FISH; preimplantation genetic testing for aneuploids (PGT-A) was performed by NGS. Patients had a low fertilization rate and a negative outcome after the first IVF/ICSI cycle, so they were advised to do chromosomal aberration analysis before their next attempt. The second IVF/ICSI procedure resulted in pregnancy, and two blastocysts were cryopreserved. The NIFTY test has shown low risk for all tested trisomies, sex chromosomes aneuploidis, and deletion syndromes, so a healthy female child was born. During pregnancy, karyotypisation results revealed that the male partner is a RobT carrier t(21;22). Sperm segregation analysis of chromosomes 21 and 22 has shown six types of sperm chromosome sets. The majority of sperm cells had a normal/balanced RobT form of a haploid set of chromosomes (68.5-76%) called an "alternate." Sperm cells that had additional chromosome 21 or 22, or lack of chromosome 21 or 22, were present in 4-12%. PGT-A performed on two cryopreserved blastocysts revealed one embryo euploid and the other with the mosaic aneuploidy of chromosome 7 present in 50% of the cells. Infertile couples with a RobT male carrier who have semen comprising of normal/alternate form in the majority have a good prognosis of IVF/ICSI outcome. PGT is recommended because of the possible occurrence of viable trisomic embryos and potential interchromosomal effect.