The developmental potential of mosaic embryos involving two chromosomes may not be inferior to that of sibling euploid blastocysts from the same cohort: clinical reflections and implications from an uncommon case.

backgroundWhether a mosaic blastocyst involving two chromosomes, each with a 45% mosaic level, can self-correct to a chromosomally normal and healthy individual post-implantation remains largely unexplored in the literature.

methodsA 35-year-old woman with unexplained infertility underwent in vitro fertilization (IVF) treatment. After multiple failed implantation attempts, one euploid female blastocyst and one mosaic male blastocyst (monosomy 11 (45%) and segmental monosomy 18 (45%) with a terminal segmental trisomy 18) were concurrently transferred in her final cycle.

resultsOf the two transferred blastocysts, only one successfully implanted. The pregnancy progressed uneventfully. Amniocentesis revealed a male fetus, indicating that the implanted blastocyst was the mosaic one. Reports of karyotype and array CGH of amniotic fluid revealed no abnormality. The patient delivered a healthy male infant at 37 + 5 weeks via spontaneous vaginal delivery.

conclusionsAccording to the COGEN position statement in 2017, mosaic blastocysts involving two or more chromosomes with mosaic levels exceeding 40% are typically ranked lowest for transfer. However, our case suggests that the implantation potential of mosaic embryos may be comparable to, if not greater than, that of their cohort euploid embryos when transferred within the same uterine environment. This observation raises the possibility that mosaic embryos possess a greater self-correction capacity than previously assumed, although further research is needed to substantiate this hypothesis.