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Pre-implantation Diagnosis

Diagnostico genético preimplantacional

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Preimplantation Genetic Diagnosis (PGD) allows us to study an embryo’s genetics, so that only healthy embryos are transferred (healthy for the particular anomaly studied).

In our assisted reproduction centre, this analysis is carried out with an embryo biopsy at the blastocyst stage. After this biopsy, the embryos are vitrified (frozen) while waiting for the results of the study, and to be transferred at a later date. In some cases it may be possible to not freeze them and perform a fresh embryo transfer.

There are two different types of PGD:

The most common is PGT-A, which is used to rule out chromosomal alterations in the embryo (such as those that cause down syndrome, or other chromosomal alterations the majority of which are incompatible with life).


The second type is PGT-M, indicated for patients who suffer from, or are carriers of certain genetic diseases. In this case, the analysis is performed to see if the embryo will result in a sufferer of the disease in question.



Age has a negative impact on egg quality, so the older the patient, the higher the percentage of embryos with chromosomal alterations. Therefore, in this group of patients PGD will be more advantageous to exclude altered embryos and increase the chances of pregnancy with a transfer of a healthy embryo.


The main cause of implantation failures and miscarriages are chromosomal alterations in the embryo, so in patients with previous treatment failures, PGD is recommended to obtain more information and increase the chances of success.


In patients with very abnormal sperm qualities, or FISH studies that show sperm with pathologies, PGD is also recommended as in these cases the number of abnormal embryos tend to be greater than the norm.

  • Healthy embryos
  • Altered embryos


  • Faster route to gestation, as embryo transfers are avoided with genetically abnormal embryos that would most probably not give rise to a pregnancy.
  • Decrease the probability of miscarriage.
  • Avoid the birth of children with chromosomal alterations.
  • Economic advantages. Although this type of analysis can increase the initial price of the treatment, in many cases the overall costs are lower. This is because we avoid the costs of unsuccessful transfers and also of embryo maintenance and storage


To carry out pre implantation genetic diagnosis a complete cycle of IVF is performed. As we have previously discussed, the technique of PGD allows us to study the genetic characteristics of the embryos before their transfer to the patient’s uterus to ensure the future baby is not born with genetically transmitted diseases.

Here we describe the different phases of the process:

Hormonal treatment for approximately 10 days so that various egg cells develop and mature, instead of one, which is what occurs in a natural cycle.

The patient has to self administer the hormones daily via subcutaneous injections. Periodic ultrasound controls and blood tests will be carried out to evaluate the maturation of the  follicles.

When the follicles reach the required size, the egg retrieval procedure  is programmed to obtain the mature egg cells, to then be able to fertilise them in the laboratory (in vitro).

It is a simple procedure that is performed under sedation in the operating theatre, and doesn’t usually take more than 10 or 15 minutes. After the procedure, the patient stays under observation in the clinic for approximately 2 hours, after which they can go home and should rest for the remainder of the day.

On the same day, our team of embryologists will analyse the eggs to perform ICSI (intracytoplasmic sperm injection) in which a sperm cell will be injected into the cytoplasm of the eggs.

After fertilisation, the embryos are cultured in special incubators in the laboratory to control their growth and development. During this process, the embryologists analyse their morphology and their number of cells to determine the quality of each embryo. The embryos are grown in the incubator during five or six days, until they reach blastocyst stage.

In this step, various cells of the blastocyst embryos are extracted and analysed in the laboratory. The cells are extracted in an embryo biopsy.

At Ovoclinic, we use the assisted hatching technique with a latest generation laser so that the embryos are not harmed and to extract the cells with greater precision and control.

Once the results of the genetic study have been received and evaluated, a healthy embryo will be transferred into the patient’s uterus. The rest of the embryos are frozen (vitrified) for future transfers.

Ten days after the embryo transfer, we perform the blood test to confirm if the patient is pregnant.


Can PGD guarantee the birth of a completely healthy child?

Nowadays there is no technique that guarantees 100% the health of a child. With the most commonly performed PGD (PGT-A), we can study the alterations in chromosomes (syndromes such as Down, Edwards or Patau), but malformations cannot be ruled out, nor genetic diseases such as cystic fibrosis, muscle dystrophy, thalassemia …

If the patient is a carrier of one of these genetic diseases, with PGT-M this particular disease can be studied in the embryo, but not all the genetic diseases that exist.

Can the embryo be damaged by performing a biopsy for the PGD?

The possibility of an embryo degenerating as a result of the biopsy is minimal. The technique is very protocolized and in Ovoclinic we have professionals with the necessary experience.

In addition, the biopsy of the embryo at blastocyst stage has proven to be a safe technique that does not harm the future baby.

Can I have healthy children if I have a genetic disease?

Depending on the type of inheritance of the disease there will be a 25% or 50% chance of having an affected child. The way to avoid this would be with DGP.

Firstly, a genetic study will have to be carried out to identify the alteration and the gene responsible for the disease. Subsequently, an informativity study is required. This study helps us to obtain the necessary information to be able to study this alteration in the embryo, and sometimes it requires the participation of patients relatives. The informativity study, once carried out, is used for all the necessary treatment cycles.