In what cases is it indicated?

• Couples at risk of transmitting chromosomal alterations or monogenic diseases.
• Couples with a medical history of repeated miscarriages.
• Implantation failure after several attempts with IVF.
• Abnormalities in spermatozoa meiosis.
• Women of advanced age.

Results

In 2006, in a world first, IVI achieved the birth of a baby to a couple in which one partner was a carrier of lymphohistiocytosis, thanks to the technique of assisted reproduction with PGT.

PGT allowed the chain to be broken in chromosomal hereditary diseases carried by 72% of the embryos analysed in 2001. As such, thanks to the study of chromosomal abnormalities through the FISH and arrays techniques, around 50% of the embryos transferred resulted in pregnancy. PCR analysis of monogenic diseases led to a 54% pregnancy rate per transfer.

PGT Techniques

For couples who have been referred due to a monogenic disease, molecular diagnosis can identify whether embryos are genetically normal or whether they will be affected by the disease which has prompted the study. For couples for whom a chromosomal study is recommended, cytogenetic molecular diagnosis allows normal or balanced embryos to be identified in terms of the chromosomes which are included in the study.

Procedure

The purpose of PGT is to analyse embryos in the laboratory following in vitro fertilisation and before they are transferred to the maternal uterus. A biopsy is performed and the embryos are analysed, allowing us to distinguish between the healthy ones and those which are affected. Allowing us to distinguish between the affected and unaffected embryos in order to improve the chances of having a healthy baby

The technique of assisted reproduction with PGT is the result of combining in vitro fertilisation with a biopsy of embryo cells by means of micromanipulation and cytogenetic molecular diagnosis techniques.

1. Preliminary phase. In this phase genetic characterisation tests are carried out on the carrier parents for the diseases to be diagnosed, with the objective of gaining as much information as possible prior to applying PGT.
2. Obtaining embryos. This involves obtaining the embryos which will undergo diagnosis. They must be generated “in vitro” using assisted reproduction techniques, even if the couple do not present any kind of reproductive problem that would prevent natural procreation.
3. Embryo biopsy. When the embryo has 6 – 8 cells. It consists of extracting one or two cells from the embryo, without compromising its normal development as a result. Once the biopsy has been performed the embryos are put back into the incubator and they stay there until the results of the diagnosis are obtained and the possibility of transferring them is assessed.
4. Genetic diagnosis and embryo transfer. The biopsy obtained is processed for analysis and a genetic study is carried out. Using the results of the genetic analysis the medical team at the Centre decides, jointly with the couple, which embryos will be transferred.

What are chromosomes and genes?

Every single cell in the human body has in its nucleus 46 chromosomes (23 from the sperm and 23 from the egg).

These chromosomes are formed of a substance called DNA which contains our genetic information. This information is distributed over thousands of tiny fragments known as genes. As such, there are two copies of every gene, one of which has come from the egg and the other from the sperm.

What abnormalities of the chromosomes and genes can cause diseases?

• Numerical alterations: this is an anomaly that affects the number of copies of a chromosome, in other words instead of there being two copies of a chromosome there are three or just one. The most well-known example is Down’s syndrome, in which there are three copies of chromosome 21 instead of two.
• Structural alterations: this is an anomaly in the contents of a chromosome, that is to say a section is out of place or missing
• Monogenic diseases: these are genetic diseases caused by a fault or mutation in a single gene. Known examples of this type of disease are Cystic Fibrosis, Haemophilia, Fragile X Syndrome, Myotonic dystrophy, and Huntington’s disease, among others.