It is a question patients often ask. With the advancing techniques in pre-implantation genetic testing (PGT) there has been much hype around embryo testing. So, should you consider paying extra for this option? It depends because there are two types of PGT.
PGT-A stands for pre-implantation genetic testing to detect aneuploidy. Simply put, it is testing embryos to see whether they carry chromosome abnormalities such as Down syndrome. As a simple analogy, it's like checking if the right number of books (chromosomes) are present in a library (karyotype). Embryos with the normal number of chromosomes are called euploid, those with an abnormal number of chromosomes are aneuploid.
Then there is also PGT-M. This stands for pre-implantation genetic testing to detect monogeneic diseases. This means that the embryos will be screened for the presence of a mutation in a gene, like the mutation that causes cystic fibrosis. To follow the previous analogy, here the geneticists will be checking the individual letters in one sentence from one of the books of the library. Because there are so many letters, the tests are currently designed to pick up mutations in parents known to be at risk.
Most people will need to consider PGT-A and we will explain the pros and cons a bit further. It is important to remember that PGT cannot make an abnormal embryo into a healthy one. So what's the point then?
If no test is carried out and an abnormal (aneuploid) embryo is replaced, it will either 1) not implant, 2) miscarry at a later stage or 3) lead to the birth of an abnormal baby if no screening is carried out during pregnancy.
The key advantage of PGT-A clearly is that only embryos that can lead to a healthy outcome will be transferred. This reduces the time-to-pregnancy (TTP). In other words, having your embryos tested or not won't change the total number of healthy babies that will be produced from one egg collection but with PGT-A a healthy live birth can be achieved in a shorter period of time.
This is the main conclusion from a large and well-conducted American study in women over 38 years of age. No differences were seen in the total number of babies born per patient 6 months after closing the study. However, the number of embryo transfers needed per live birth was lower in the PGT-A group compared with the control group (1.8 vs. 3.7), as was the time to pregnancy (7.7 vs. 14.9 weeks). This is mainly because the number of miscarriages was much lower in the PGT-A group (2.7% vs 39.0%). While it was not mentioned in the study, another implication is that the cost of testing is often outweighed by the saving of not having to undergo unnecessary embryo transfers.
It is, however, less clear whether the benefits are still this obvious for younger women (<34 years). The reason is that the eggs of younger women are a lot less likely to have already developed chromosome problems. Aneuploidy in eggs dramatically increases with age. Read more about the STAR trial here.
Click here to watch the Monash IVF Genetic Screening Information Webinar.