What is Preimplantation Genetic Diagnosis?
Thanks to this diagnostic technique, we can practically ensure that your baby will be born healthy. We genetically analyze the embryos before starting the transfer to determine which one is most suitable.
How is it done?
The diagnosis is done with an embryo biopsy, which involves obtaining cells from the embryo when it is only five days old (blastocyst).
These are the phases of the PGD:
- Ovarian stimulation and in vitro fertilization. This is only done as part of an IVF process. In this treatment, the first step is to stimulate the ovaries to fertilize the eggs and create the embryos.
- Embryo biopsy. Technique in which the cells of the most viable embryo are extracted.
- Analysis of the biopsy. Once the embryo is biopsied, it is kept in the incubator under stable CO2, O2, humidity and temperature conditions for its correct development, while the genetic laboratory performs the necessary studies for each case and awaits the results.
- Transfer of embryos. The results are ready after 24 hours and, in some cases, the embryo can be transferred in the same cycle. In others, the embryos have to be vitrified and transferred in the next cycle.
What types of PGD are there and what do they detect?
The PGD can detect chromosomal and genetic abnormalities:
PGD to detect aneuploidies, or PGS
Checks the embryos for the right number of chromosomes. An abnormality can result in the embryo being unable to implant in the mother’s womb or unable to grow (miscarriage or non-developing pregnancy), or being born with Edwards Syndrome or Down Syndrome.
This screening increases the chances of pregnancy, decrease the chances of a miscarriage and raises the odds of having a healthy child.
It is especially recommended when:
- The woman is over 37 years old and wants to use her own eggs.
- The male has a low sperm count: severe oligospermia diagnosed.
- There are chromosomal abnormalities in the semen: FISH diagnosis in pathological semen.
- The couple presents a long-term infertility.
- There is a history of two or more repeated miscarriages.
PGD for structural abnormalities (altered karyotypes)
Cells in the human body have 23 pairs of chromosomes but, in a certain percentage of the population, it may be that:
- There are swapped chromosomes: chromosomal translocations
- There are inverted chromosomes: chromosomal inversions
- A small chromosome fragment is missing: chromosomal deletions
- Other alterations in the karyotype.
When this happens, the person is healthy but their reproduction can be affected, leading to a greater number of miscarriages or births with some chromosomal rearrangement. The PGD study makes it possible to select those embryos that have not inherited any of the abnormalities in the karyotype.
PGD for hereditary diseases
Done when the consulting partner is a carrier or is affected by some type of monogenic disease (such as Cystic Fibrosis). This technique allows selecting those embryos that have not inherited the genetic component that causes the disease.