Preimplantation genetic testing (PGT) is the testing of early stage embryos (up to 5 days old) for genetic abnormalities.
The term “preimplantation” is used because testing is performed on embryos during the time before they would naturally implant into the uterus (usually after day 6). PGT is offered as a complement to a patient’s in vitro fertilization (IVF) treatment.
PGT is comprised of two different types of tests, namely preimplantation genetic diagnosis (PGD) and preimplantation genetic screening (PGS).
The Preimplantation Genetic Screening (PGS) test offered by Next Biosciences, EmbryoSx, is offered as a complement to a patient’s in vitro fertilisation (IVF) treatment, to improve pregnancy success rates and reduce miscarriages. PGS is testing of early stage embryos for chromosomal abnormalities.
Imagine DNA as a piece of string. If you coil the DNA, it would form a structure called a chromosome.
Humans have 23 pairs of chromosomes (46 in total) within almost every cell in our body.
Unfortunately, human biology is not without its flaws. Several factors (such as maternal age) can affect the number of chromosomes in a sperm or egg. Instances can (and do) arise where missing or extra chromosomes are present in the sperm or egg, and subsequently leads to an abnormal number of chromosomes in the embryo/foetus. Abnormal chromosome numbers are associated with either miscarriage (as they are not compatible with life) or a genetic condition (such as Down syndrome).
Preimplantation Genetic Screening (PGS) is a test that comprehensively screens all the chromosomes (Chromosome 1-22 and the sex chromosomes) in an embryo biopsy sample for any extra or missing chromosomes, and large deletions or duplications of genetic material. Selecting embryos with the correct number of chromosomes for transfer has been shown to significantly improve implantation outcomes and pregnancy success rates.2 As a result, PGS is recommended by many top fertility specialists.
Studies have shown that IVF pregnancy rates can be increased with PGS, when compared to IVF cycles that did not include PGS.
Preimplantation Genetic Screening (PGS) is a test that comprehensively screens all the chromosomes (Chromosome 1-22 and the sex chromosomes) in an embryo biopsy sample for any extra or missing chromosomes, and large deletions or duplications of genetic material. These chromosome abnormalities usually result in pregnancy failure (as they are not compatible with life), or can result in a genetic condition (such as Down syndrome, Patau syndrome, Edwards syndrome, Turner syndrome or Klinefelter syndrome).
PGS is available to any patient, but is typically prescribed for couples where the female patient is of advanced maternal age; patients who have suffered recurrent pregnancy losses both naturally and/or through IVF; or patients who have a known familial translocation/inversion, gene duplication or deletion.
In order to screen the chromosomes in an embryo, a biopsy is performed by an embryologist at your IVF centre. The biopsy removes 3-5 cells from the embryo, which are then sent to Next Genetics, where they are screened for chromosomal abnormalities. The sophisticated and validated technology used at Next Genetics is accepted by the European Society of Human Reproduction and Embryology (ESHRE).
Yes, scientific studies have shown that embryo biopsies do not add risk factors to the health of babies born after IVF with PGS.2
No test can guarantee that a baby will not have any medical issues. PGS does not test for all genetic and non-genetic problems that may be present in an embryo. Genetic counselling before and after testing is recommended.
1 Yang et al. (2012). Molecular Cytogenetics 5:24
2 Liebaers et al. (2010). Human Reproduction 25:1
3 Hodes-Wertz et al. (2012). Fertility and Sterility 98:3
4 Yang et al. (2013). Molecular Cytogenetics 6:32