Pre-Implantation Genetic Diagnosis

PGD

What is PGD?

Pre-implantation genetic diagnosis is a diagnostic technique that allows us to identify abnormalities in an embryo’s genes or chromosomes before it is transferred to the uterus. This means that children are born healthy and we can eradicate family genetic pathologies.

What is the process?
What is technique is used to analise?

El primer paso que los pacientes deben seguir, es acudir a un centro de Reproducción Asistida donde los especialistas, genetistas, embriólogos y ginecólogos, realizarán un estudio completo de su historia familiar y analizarán todas las pruebas, con el fin de dar a los pacientes el consejo genético más apropiado para ellos, y apoyándose en él, proponer el tratamiento más adecuado para su caso. La comunicación con los pacientes durante el consejo genético previo al DGP debe ser muy clara, concisa y, por supuesto comprensible. Nosotros ofrecemos este tratamiento siempre que el diagnóstico genético sea técnicamente posible, su fiabilidad sea elevada, las posibilidades de éxito sean aceptables y las técnicas de reproducción asistida sean factibles.

Una vez decidido el tratamiento a seguir, y siempre y cuando se indique el Diagnóstico Genético Preimplantacional (DGP), se deberá realizar una fecundación in vitro, para posteriormente realizar la biopsia del embrión. La biopsia embrionaria se lleva a cabo cuando los embriones alcanzan el estadio de desarrollo de 6 a 8 células, al tercer día de cultivo, o en el de blastocisto, quinto día de desarrollo. Consiste en hacer una pequeña incisión en la zona pelúcida del embrión (si comparamos el embrión con un huevo, la zona pelúcida vendría a ser como la cáscara) y extraer una célula, blastómera, en el caso de la biopsia en el tercer día, o un trozo de trofectodermo, cuando se realiza al blastocisto. En el núcleo de estas células se encuentra toda la información genética del embrión, por lo que al analizarla, sabremos que le ocurre a éste. Este procedimiento no afecta a la calidad de embrión y después de él seguirá su desarrollo de forma totalmente normal, como si nada le hubiese ocurrido.​

In Tahe Fertilidad we use the Array-CGH (Comparative Genomic Hybridation) technique to analyse the embryo. By using this test, we obtain the full study of the genoma which provides information about the genetical material gains and losses. It is a quick and realible technique and the results can be avalaible in less than 48 hours.

EmbryoARRAY® allows the study of 23 pairs of chromosomes, in contrast to the 9 pairs that it was used to be studied a few years ago under the FISH technique. Array-CGH will detect chromosomal regions that are affected by deletions and duplications very efficiently, throw the use of array scanning.

This technique has a higher reliability and lower false positive and negative rates than any similar test in the market (98% efficiency), that is why it has been the technique of our choice in Tahe fertilidad.

XX. Embryo with normal chromosomal development.

42, XX, -1,-4,-8, -16. Embryos with chromosomal abnormalities of chromosomes 1, 4, 8 and 16.

24 to 48 hours after the embryo biopsy, we can transplant the healthy embryo into the uterus, and the embryonic treatment is complete. Once this is done it is just a matter of waiting for the embryo to implant itself in the uterus. Leading to pregnancy and a baby that will neither suffer from the inherited illness nor pass it on to future offspring. The illness is thus eradicated from the family genes.

Which patients benefit from PGD?

Repeated failure of implantation

Patients who have not become pregnant after several embryonic transplantations with healthy embryos. In these cases we carry out a genetic analysis to determine if a significant number of embryos have an abnormal number of chromosomes. This may be causing the problem.

Women of advanced reproductive age

The risk of chromosome abnormality increases with age, as older eggs are more likely to reproduce chromosomes incorrectly in cells. This can result in embryos with abnormal chromosomes, which in turn can lead to repeated failure with implantation, problems with the foetus, or miscarriage.

History of spontaneous miscarriage

In patients who present no other explanation of the problem, it has been found that chromosome abnormalities account for 50% of miscarriages.

Men with a very low sperm count

It has been found that there is a significant increase in chromosome abnormalities in sperm in a high percentage of men with a low sperm count, which can lead to embryos with chromosome defects. Patients with indications of abnormal sperm are advised to undergo a chromosome study before treatment using the FISH technique, and if this shows a high number of cells with an abnormal chromosome count we would recommend PGD.

Translocation, inversion and other chromosome abnormalities

Problems relating to chromosome structure or balance will have no clinical manifestation, but can result in gametes, eggs or sperm with an unbalanced number of chromosomes, which may produce abnormal embryos and unsuccessful implantation, miscarriage, or children born with genetic illnesses.

Monogenetic illnesses

Monogenetic illnesses are due to genome mutations, which depending on whether they are inherited in the dominant or recessive form, can affect foetuses in different ways. To detect these illnesses in embryos we use highly complex techniques in molecular biology. It is currently possible to diagnose many monogenetic illnesses in the embryo, including cystic fibrosis, Duchenne and Beckett muscular dystrophy, fragile X syndrome, thalassemia, falciform anemia and Marfan syndrome.

Did you know ...

… Karyotype is the metaphysical arrangement of chromosomes in a cell according to its size and morphology . a human cell has 46 chromosomes, in 23 pairs, arranged in 22 autosomal pairs and one sexual pair (men 46XY and women 46XX).