We’ve been doing the Creating a Family radio show since 2007. In that time, I’ve interviewed hundred of expert on hundreds of topics, but of all these topics, I think the biggest changes I’ve seen in these past 8 years has been in the area of genetic testing of embryos for in vitro fertilization. The medical advances have been remarkable.
I can remember back to 2008 when we had an embryologist on the show that described genetic testing as more art than science. Boy, times have changed.
Not only have there been improvements to genetic screening, but also to the cryopreservation techniques for embryos (embryo freezing) that allow for later testing. According to Dr. Jessica Mann, with Reproductive Science Center of New Jersey and our guest on this week’s Creating a Family show, there are significant advantages to doing a biopsy on a Day 5 embryo (blastocyst) over doing a biopsy on a Day 3 embryo. The problem with Day 5 testing is that it may mean missing the implantation window, but since success with frozen embryo transfers now rivals fresh transfers and may even be better, this is less of a problem.
Who Should Do Pre-Implantation Genetic Testing
Genetic testing on embryos may well become part of the standard IVF protocol in the future, but for now it is most often recommended for the following groups:
- Women who have experienced multiple failed IVF cycles.
- Women who have experience more than 2-3 miscarriages.
- Women over the age of 35 or 38 (doctors differ on what age).
- Couples who are carriers for genetic disorders.
Risks of Genetic Testing to the Patient
Embryonic genetic testing poses minimal tangible risk to the parents. Unfortunately, this may be accompanied by a great deal of stress and uncertainty. At the time of preimplantation genetic testing, the eggs have already been removed from the patient and therefore, the test itself does not add any further risk to the parents.
Risks of Genetic Testing to the Embryo
In order to test an embryo, a few cells need to be removed from the embryo. This has potential risks which have not been fully evaluated since the technique is too new to have good long term research. So far, the data has not shown a detrimental effect on the embryo.
It is expected that embryo biopsies on Day 5 will result in less risk to the embryos. Day 3 biopsies have been shown to potentially disturb embryo development and may lead to poor growth in culture.
Day 3 biopsies have a higher error rate (about 5%) than day 5 biopsies. This may lead to reporting a normal result when the embryo is abnormal or vice versa. This problem occurs because of mosaicism. The term mosaicism describes the presence of more than one genetic make up of the embryo. With time, the embryo may “self correct”, but patient have no way of knowing if that will happen.
Additionally, a previous commonly used genetic testing technology, FISH, was associated with a lower live-birth rate. Currently, most centers use array CGH, PCR based technology, SNP arrays, or NGS technology. Unfortunately, there is no study directly comparing these various technologies in terms of live-birth data and/or perinatal or postnatal risks to the child.
My thanks to Dr. Jessica Mann for the info on the risks of PGS to the infertility patient, the embryo, and the child. Check out this Creating a Family show. I loved Dr. Mann’s delivery and her ability to make a complex topic easy to understand.
Image credit: Josh*m