IVF

There are 2 types of genetic testing, which can be performed in addition to the In-Vitro-Fertilisation (IVF) or Intra-cytoplasmatic-sperm-injection (ICSI) treatment to study the genetic material of an embryo before it is transferred into the womb.

  • Preimplantation Genetic Screening (PGS) which is done to screen for abnormalities in the number of chromosomes in the embryos in unaffected parents
  • Preimplantation Genetic Diagnosis (PGD) the aim is to detect whether a genetic abnormality, present in one of the parents affects the embryos, because then the disease would be passed to the offspring.

     

    PGS is recommended for:

    • Repeated IVF failure- especially if the transferred embryos were of good morphological quality, in that case a genetic disorder might be the reason of the treatment failure
    • Women above the age of 35 -to improve the chance for a successful pregnancy and a healthy child
    • Severe male factor -as a weak semen sample often implies a genetic abnormality of the sperm, which will cause genetic abnormality for any resulting embryos
    • Recurrent abortion: patients with repetitive miscarriages (3 or more)

    PGD is recommended for:

    • Couples with inherited diseases in family history as by performing PGD for that disease affected embryos will be eliminated
    • Repeated miscarriages due to genetic disorders
    • Couples who have a child with genetic disease
    • Gender selection in the case of a gender linked hereditary disease
    • Consanguinous couples (related couples, who might carry genetic abnormalities)

    Embryo biopsy will take place on day 3 (after insemination or ICSI) or day 5, where 1 or 2 blastomeres (cells) will be taken from a day 3 embryo or multiple cells from a day-5 blastocyst. These cells contain the genetic material of the embryo, which will be sent to the Genetic Laboratory for analysis. The type of test performed depends on the reason PGD was recommended for.

    FISH-technique: Fluorescence in situ hybridisation (FISH) provides researchers with a way locate and visualise a specific gene or DNA(Deoxyribonucleic acid is a molecule that encodes the genetic information of a human being) sequence using fluorescent probes. The fluorescent probes bind to specific areas on the chromosomes and detect any alterations that may cause a genetic condition.

    It can be used to detect small deletions and duplications that are not visible using microscope analysis. This test doesn’t screen all the chromosomes, only the chromosomes with the most frequent disorders and it is recommended e.g. for couple’s with repeated failures and miscarriages, gender selection, down syndrome.

    PCR-technique: A PCR or polymerase chain reaction is a laboratory procedure in which millions of copies of a specific piece of DNA (Deoxyribonucleic acid is a molecule that encodes the genetic information of a human being) is made. PCR can be used in the analysis of gene mutations that are linked to many genetic diseases including - cystic fibrosis, sickle cell anaemia, phenylketonuria, muscular dystrophy.

    aCGH-technique: Array Comparative Genomic Hybridization (aCGH) is a method of genetic testing that allows the whole genome (all the genetic material present) to be analysed. It identifies minute alterations in chromosomes that would not be seen by a microscope.It can be used to quickly scan an entire genome for imbalances that may cause a genetic condition.

    NGS: Next-generation sequencing applies to genome sequencing, and resequencing. It seems to be slightly more accurate that the aCGH, however, more research is required to confirm these findings.

    Single gene Analysis: for specific inherited diseases, such as Thalasaemia, Cystic fibrosis.

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