Preimplantation Genetic Testing (PGT-A, SR, M)

Today, the genetic material of embryos can be examined before implantation. This is typically done on day 5 or 6, and the harvested cells are genetically analyzed in a highly specialized laboratory. For couples with a pre-existing hereditary disease, such as cystic fibrosis, the method is referred to as PID (preimplantation genetic diagnosis) or PGT-M (preimplantation genetic testing for monogenic disease); if, on the other hand, all embryos are tested for new mutations such as trisomies or monosomies, we refer to it as PGT-A (preimplantation genetic testing for aneuploidy, aneuploidy screening, formerly known as PGS). PGT-A is used much more frequently than PGT-M, which is why the following text focuses primarily on PGT-A (and the technically identical PGT-SR for couples with so-called translocations).

PGT-A has been permitted in Switzerland since September 2017 (unlike in Germany and France, for example). We have relied on this method from the very beginning and have since developed a high level of expertise, particularly within our team of biologists. See also our page on IVF add-ons.

Who is a candidate for PGT-A?

• Women over 35
• Women who have experienced miscarriages
• Women who have had embryo transfers without implantation
• Desire to avoid transferring embryos with an abnormal number of chromosomes

How does PGT-A work?

• No immediate embryo transfer
• On day 5 or 6, well-developed embryos are biopsied and frozen
• Four weeks later, the first embryo with normal genetic material (euploid embryo) can be transferred
• Success rates at Singer IVF: approximately 60% live births, virtually independent of age
• However: only about 60% of women aged 41–42 have an embryo transfer at all per cycle; the rest lack suitable embryos

Additional costs for PGT-A

• Depending on the number of embryos tested
• usually 3,200–3,800 Swiss francs
• These additional costs apply only if blastocysts suitable for biopsy have formed by day 5 or 6

Normal human genetic makeup

Even at a young age, the majority of naturally formed embryos deviate from the normal number of chromosomes, mostly because the female egg cell passes on two copies of a chromosome (leading to trisomy) or none at all (leading to monosomy) to the embryo instead of just one. These numerical abnormalities are referred to as de novo mutations, or more precisely, non-disjunction; the resulting embryos with numerical abnormalities are aneuploid. Their frequency increases exponentially with the woman’s age; this is the biological basis for the sharp decline in fertility as well as the increasing frequency of miscarriages beyond the age of 35.

Analysis of over 2,500 biopsied embryos in our laboratory reveals a striking correlation between age and the genetic “health” of embryos grown in vitro:

Summary

• Preimplantation genetic testing with aneuploidy screening (PGT-A) is a promising, modern, and legally permitted option in Switzerland for IVF couples facing difficult situations and/or time constraints. The primary motivators are being over 35 years of age and a history of miscarriages.
• Not all IVF couples will opt for PGT-A—if only because of the effort and cost involved—but for the patient groups mentioned above, it represents a major advance.
• PGT-A identifies embryos that would otherwise have no chance of success and would have led to failed attempts or miscarriages.
• PGT-A improves the success rate of difficult treatments, shortens the time to pregnancy, prevents painful miscarriages, and can make the difference between starting a family and remaining childless for older women.
• The older the woman and the smaller her ovarian reserve, the greater the risk that no embryos suitable for transfer will develop during a single cycle.