For infertile patients
Why is it important to test IVF embryos?
Many pregnancy attempts fail because the embryos have chromosomal abnormalities. Most of the time, these abnormal embryos (with too many or too few chromosomes) do not become pregnant or end in a spontaneous abortion within the first trimester or, in a small percentage of cases, they evolve but give rise to a child affected by some pathology.
These are abnormalities that cannot be detected with the naked eye by microscopic observation. To identify them, it is necessary to genetically analyse the embryos by means of the Preimplantational Genetic Test (PGT), which is the technique previously known as Preimplantational Genetic Diagnosis (PGD). In this way we can transfer only embryos without anomalies to the woman and therefore:
- Increase the possibility of pregnancy.
- Decrease the risk of miscarriage.
- Reduce the risk of having to resort to therapeutic abortion.
Who is particularly interested in PGT?
- Women over 37 years of age
- Couples with two or more previous IVF cycles without pregnancy.
- Couples with previous miscarriages (with 2 or more miscarriages)
- Males with seminogram alterations
- Males with pathological meiosis or altered FISH in spermatozoa
- Women/males carrying chromosomal rearrangements
From the age of 37, is it always advisable to perform a PGT?
Yes. The risk of chromosomal abnormalities increases as maternal age increases. By the age of 35 the ovaries have aged, only 10% of the eggs are left and the fewer eggs that remain, the poorer their quality. This ageing of the ovarian reserve translates into an increased risk of the oocytes distributing the chromosomes to the daughter cells incorrectly. The vast majority of chromosomally altered embryos block their development before implantation or within the first trimester of pregnancy. Ultimately, a large proportion of these embryos either do not result in pregnancy or result in miscarriage.
| Maternal Age | % Altered embryos |
| 35-37 | 70% |
| 38-41 | 78% |
| 42-45 | 92% |
Only a small percentage of chromosomal alterations are compatible with life. Thus the risk of having a child affected by a chromosomal abnormality in the general population is:
- 1/385 at 30
- 1/179 at 35
- 1/63 at 40
- 1/19 at 45
Can any couple request a PGT?
Yes. More and more couples are requesting PGT to increase the chances of pregnancy in their cycle and reduce the chances of miscarriage. It must be taken into account that among couples without fertility problems, more than 20% of the embryos already present some type of chromosomal abnormality and these cannot always be detected by observation in the laboratory.
How is PGT performed?
- In Vitro Fertilisation to obtain the embryos.
- Embryo biopsy. The biopsy can be carried out during the third day of embryo development or between the fifth and sixth day when it has reached the blastocyst stage.
- Diagnostic genetic analysis. The sample obtained by biopsy is processed for analysis and subjected to genetic study by NGS.
- Embryo transfer. The result of the genetic analysis is transmitted to the assisted reproduction team by means of a detailed report and a decision is made as to which embryos will be transferred depending on the PGT result and the morphological characteristics of embryo viability. If the biopsy is performed on the third day of development, the embryo transfer to the maternal uterus can be performed immediately after the analysis, normally 5 days after the recovery of the oocytes. In cases where the biopsy is performed between the fifth and sixth day of development, it will be necessary to freeze the embryos and schedule the transfer at a later date.
Can PGT damage the embryo?
It is a very sophisticated technique but performed by expert biologists does not adversely affect the development of the embryo.
Are all the chromosomes in the embryo analysed?
Yes. At Institut Marquès we analyse all the chromosomes of the embryo.
Does PGT increase the probability of pregnancy?
Yes, because it allows us to transfer only genetically or chromosomally normal embryos to the patient. This doubles the chances of pregnancy.
Does PGT reduce the chances of miscarriage?
Yes, as most miscarriages are due to chromosomal abnormalities.
Is it indicated in patients with 2 or more miscarriages?
Yes. It can prevent further miscarriages as 60% of repeat miscarriages are due to a chromosomal cause.
Does prenatal diagnosis have to be done after a PGT cycle?
Yes. PGT is not an alternative technique to prenatal diagnosis. Prenatal diagnosis (amniocentesis or chorionic villus sampling) is always recommended for patients after an IVF and PGT cycle, as it has a reliability of 92%.
