Over half of our patients doing IVF opt for PGT. PGT involves biopsying blastocyst embryos (typically day 5-7 embryos) and sending the cells to a genetic testing lab for analysis. The lab analyzes the cells to determine how many chromosomes the cells have and whether there are any large pieces missing or duplicated.

At Olive, the lab we use is called Sequence46 which is based in LA, California. Sequence46 provides us a report on the PGT embryos. Each embryo is reported as:

Euploid: We consider this a chromosomally normal embryo. Technically it means that < 30% of the chromosome material was abnormal. These embryos have about a 60% chance of a livebirth.

Aneuploid: We consider this a chromosomally abnormal embryo and generally do not recommend using this embryo.  Technically it means that > 70% of the chromosome material was abnormal. The live birth rate is 0-1%.

Mosaic: Some of the cells are chromosomally normal and some are chromosomally abnormal. Technically is means that between 30-70% of the cells are abnormal. Many of these embryos are actually “normal." When we biopsy the embryo we are not biopsying the baby (called the inner cell mass) but the trophectoderm (the future placenta). In some instances, the placenta has some cells with abnormal chromosomes, but the inner cell mass (the baby) does not; or the inner cell mass does have some abnormal cells, but they will “die off” and be replaced by normal cells.  Mosaics have between a 20-40% live birth rate, depending on the type of chromosome issue.

Segmental Aneuploidy: A segment of a chromosome is missing or duplicated. If the section is missing in all cells (called full copy segmental aneuploidy), we generally do not recommend using that embryo as the child may have a serious genetic issue. If the section is missing in just some cells (called a mosaic), we discuss using this embryo as it is much like the mosaic embryos above they inner cell mass (baby) may very well be normal.

It is fairly recent that segmental aneuploidy have been reported. As the testing lab gets better and more detailed in their testing, we will be getting more and more information about embryos which is exciting and can be overwhelming. 

I hope this guide is useful as you review your PGT results with your Olive genetic counsellor or physician.