FAQ

A mosaic embryo is an embryo with both normal (euploid) and abnormal (aneuploid) cells. The normal, euploid cells have the correct number of chromosomes (46 chromosomes) while the abnormal, aneuploid cells have extra or missing chromosomes. The mosaic level refers to the inferred percentage of aneuploid cells in the TE biopsy specimen. Typically, they are reported as either "high" or "low" The mosaic type refers to the nature of chromosomal abnormality. There are four types of mosaicism: segmental, one chromosome, two chromosome, and complex.

Trophectoderm (TE) biopsy allows us to collect trophectoderm cells from the embryo at the blastocyst stage. Trophectoderm cells comprise the wall of the cell wall and eventually develop into the placenta. These cells then undergo a pre-implantation genetic testing for aneuploidy (PGT-A) to measure the embryo's level of mosaicism. The cells are tested for extra or missing chromosomes, both of which are indications of aneuploidy.

Pregnancy outcomes depends on the level and type of mosaicism. Genetic counsellors can use the mosaic embryo calculator located in the "For Professionals" page to calculate a relative score for the implantation/ongoing pregnancy rate of a specific embryo. The degree of mosaicism also interacts with other parameters to affect pregnancy outcomes.

Follow this link to find a genetic counselor (Canada and USA only). A genetic counselor will guide you through prenatal/postnatal testing and discuss next steps.