Preimplantational Genetic Diagnosis

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Preimplantational Genetic Diagnosis (PGD) is the study of chromosomal and genetic abnormalities in the embryo before its transfer to the recipient mother.

PGD allows us to know which embryos are free from chromosomal anomalies and genetic mutations. Its aims are to ensure healthy offspring and to stop the transmission of certain pathologies.

The PGD technique as well as its use is set out in Spanish Law 14/2006 of May 26 regarding assisted human reproduction techniques.

The first step involves an exhaustive study of each case by our geneticists and molecular biologists. Then a personalised diagnostic strategy for the future embryos is decided.

The couple must undergo an In Vitro Fecundation (IVF) treatment. and microinjection (ICSI technique) is advised in order to fertilise the ovocytes. There is a waiting time of three days to ensure that the embryos resulting from the process have divided correctly to the stage six-eight cell stage. At this point embryo biopsy takes place; however, if the six-eight division has not been achieved, biopsy is not recommended as it reduces the viability of the embryo. Thanks to the experience of our team and the use of a micro laser only one cell is extracted (a blastomere), so that the future embryo is not damaged and that the implantation rate is not reduced, having already been reduced during the biopsy.

The extracted blastomeres are analysed in the Molecular Biology laboratory and the biopsied embryos remain in culture until the genetic diagnosis has been achieved. The goal is to transfer healthy and evolved embryos that will produce a totally normal pregnancy.

Currently the technique is used to detect:

1. Autosomal or sex-linked chromosomal hereditary diseases

The number of hereditary diseases where we understand the origin of its anomaly is growing every day. When we can detect if the embryo is affected or not, we can assure healthy offspring and stop the transmission of the illness to future generations.

The genetic department at Instituto Bernabeu offers a comprehensive study of your family and delivers a diagnosis faster than at any other centre.

Our department is a pioneer in this field and represents a worldwide point of reference in the MDA technique (Multiple Displacement Amplification) used in Preimplantational Genetic Diagnosis. The development and practice of this technique at Instituto Bernabeu has solved one of the main limitations of PGD specifically relating to monogenic diseases which is the quantity of DNA available to carry out the diagnosis.

To date the diseases that we have already diagnosed are:

  • Huntington´s Chorea
  • Fragile X Syndrome
  • Miotonic Distrofy
  • Marfan Syndrome
  • Retinoschisis
  • Haemophilia
  • Cystic Fibrosis
  • Beta Thalassemia
  • Hydrocephaly
  • Emery-Dreyffus
  • Incontinentia Pigmenti
  • Acute Intermittent Porphyria
  • Adrenoleukodistrophy
  • Spinocerebellar Ataxia type 3
  • Duchenne Muscular Dystrophy
  • Hypocalcemia
  • Hereditory Angioedema
  • Carney Syndrome
  • Spinal Muscular Atrophy Type 1
  • Charcot- Marie- Tooth Type 1
  • Polycystic Kidney Disease

If you would like to have more information regarding any other disease which does not appear on the above list, do not hesitate to ask us, as we are constantly designing new PGD protocols for other diseases. It is for that reason that the above list is constantly growing. The versatility of both the equipment in the Genetic department and of our staff allows us to carry out different types of research into other hereditary illnesses. In this way, we can offer a service which is personalised to each patient.

2. Structural chromosomal abnormalities

There are no clinical repercussions relating to individuals who have structurally-balanced chromosomal abnormalities (translocation, inversion, etc.). The importance of being a carrier of a structurally-balanced abnormality is that the oocytes or spermatozoids produced can have a chromosomal imbalance. Therefore the resulting embryo or pregnancy will inherit this imbalance, causing failure at the implantation stage, or miscarriage or even the child to be born with physical and/or mental disabilities. Patients with this kind of abnormality may suffer multiple miscarriages or have children born with fatal syndromes. Using PGD along with the FISH technique and specific catheters to isolate the chromosomes involved, permits the selection of embryos that lack the imbalance, thus obtaining a successful pregnancy.

3. Recurrent miscarriages

It is believed that in 50% of all recurrent cases of miscarriage, the fault is with the embryo and not with the couple.

An anomalous number or an altered structure of the embryo chromosomes is one of the explanations attributed to many cases of recurrent miscarriage. PGD, by means of the FISH technique, allows the selection of embryos free from these structural and numerical anomalies (analysis of 9 chromosomes X, Y, 13, 15, 16, 17, 18, 21, 22). A successful pregnancy can then be achieved.

4. Previous failures at IVF

Sometimes the embryos transferred in an IVF cycle may seem normal but they can have chromosome disorders that are not diagnosed during a conventional IVF treatment. This could explain failure at the implantation stage.

In the above mentioned cases, PGD is especially important because it not only allows a more accurate embryo selection but also can help in the decision to continue or start other IVF treatments.

5. Older women

There is evidence of an increase of aneuploidy in pregnancies borne by older women. Thanks to PGD we can avoid the transfer of those embryos that are morphologically normal but that could be chromosomically altered.

6. Research into altered chromosomal segregation in spermatozoids (FISH or meiosis)

The male factor is one of the causes of a high level of aneuploidy in the embryo. Previous genetic research of spermatozoids with an alterated result indicate a bigger risk of aneuploidic embryos. PGD, as in the above-mentioned cases, allows us to distinguish between the chromosomically altered embryos and the normal ones.

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