We can certainly eliminate the risk of down syndrome, three copies of the chromosome 21, using pre-implantation genetic testing at IVF and this is very important for cases and pregnancy of high risk due to increased maternal age or chromosomal rearrangements which includes chromosome 21. Those cases it is very useful to use the tool of the pre-implantation genetic test. In any case, it is critical to keep in mind that the pregnancy should be considered and should be monitored as all the other pregnancies at the prenatal testing procedure.
My personal answer is that we cannot avoid it one hundred percent. We have cases of misdiagnosis through PGT-A formerly known as PGS that down syndrome was the result of a transfer of a chromosomally normal embryo. This is because PGT-A/PGS is not a one hundred percent test, however most of the labs that are carrying out PGT-A with NGS have a very high diagnostic rate so most of the time you have a very good chance of avoiding trisomy 21 which is down syndrome. But this can never go, up till now, to one hundred percent.
I wouldn’t say you can avoid Down syndrome 100% with IVF. There is still a minimal risk of misdiagnosis; however, it can reduce the risk of having a Down syndrome baby.
A 40-year-old individual has a 2.5% risk of developing a pregnancy that is a carrier of Down syndrome, both naturally and through IVF. If you carry out pre-implantation genetic testing, you remove 98% of that 2.5% risk. It becomes a minimal risk for an individual or couple.
Yes, you can detect trisomy 21 or Down syndromes in embryos if you do PGS on them. There are 3 types of PGS. One of them detects if the number of chromosomes is correct or not. You can also detect if there are translocations or if the chromosomes have exchanged parts of them, or you can check if there are mutations inside the chromosomes.
From these 3, the first one is so-called PGT-A because we are detecting aneuploidies, and these are all abnormalities where the embryo has extra chromosomes or lacks one chromosome. If they have an extra chromosome, that’s called a triploidy.
If the embryo only has one chromosome, it’s called Monosomy, and all these abnormalities either in excess or because the embryo lacs that chromosome can be detected by the PGS.
