We report a case of normalization of mosaic embryo transfer resulting in the successful delivery of the healthy live baby. The patient was having advanced maternal age and poor ovarian reserve and previous implantation failure. The conventional peripheral blood karyotypes of the couple were normal46, XX, and 46, XY. The patient underwent infertility treatment at our centre, ovulation was triggered and three oocytes were retrieved which developed into blastocysts. The trophectoderm cells were biopsied on day 5 after fertilization and were subjected to Preimplantation Genetic Screening (PGS) using next generation sequencing (NGS) for the detection of the presence/absence of any chromosomal aneuploidy in the embryos.

The whole genome analysis for three embryos showed that the first was complex aneuploid, the second was chaotic aneuploid and the third embryo was mosaic (<40%). After careful consideration and in absence of any other option, the intervention was made and the embryo with mosaicism of chromosome 3 was transferred after taking the couple’s consent. Prenatal and postnatal follow-up was done, no pathological findings were reported and the foetus was observed with absolutely normal growth during pregnancy and a phenotypically and genotypically normal healthy baby was delivered after 36 weeks and 2 days. The blood karyotype of the baby and aneuploidy screening using NGS showed the normal chromosomes of the baby validating the normalization or self-correction of the mosaic embryo.

Our study suggests that PGS assisted In Vitro Fertilization (IVF) treatment has paved the way for undertaking appropriate clinical risk calculation for the transfer of potential mosaic embryos resulting in a healthy euploid embryo.

Keywords: Embryo, In Vitro Fertilization (IVF), Postnatal, Prenatal, Preimplantation genetic screening. Mosaicism, euploid, Aneuploid,

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Dr Alpana Razdan

Vice President and Head Lab Services, Gene strings Centre for Medical Genetics, New Delhi 110017