The Preimplantation Genetic Diagnosis (PGD) is a technique used to test embryos for genetic or chromosomal disorders before it implants in the uterus and can be combined with an IVF cycle.

It involves a biopsy where a cell is removed from an embryo at an early stage of development, generally on day three after the fertilization. The cell is then analyzed to determine the presence of specific genetic or chromosome features. During the study the embryos are kept in a culture medium in the laboratory until the results are back.

Once the genetic or chromosome diagnosis is back we will select the normal embryos to transfer or freeze them and will discard the abnormal ones.  

PGD is a useful tool to avoid the transmission of genetic abnormalities or hereditary diseases to the offspring, eliminate the risk of spontaneous miscarriages in some particular cases and improve the success rates of IVF treatments.

In IVF treatments with PGD the embryos will be selected bases on their morphology and chromosomes. This increases the chances of getting pregnant as we minimize the risk of transferring abnormal embryos which generally do not implant or produce spontaneous miscarriages.

Despite being a technique that allows an accurate diagnosis, PGD has some limitations that make question its effectiveness in some cases.

For this reason PGD should not exclude prenatal testing.  

PGD is recommended in:
- Patients that are carriers of chromosomal alterations (translocations,    inversions or other chromosomal disorders)
- Patients with a history of recurrent miscarriages
- Patients with repeated IVF failure
- Patients with previous trisomic pregnancies
- Patients with risk of transmitting monogenic diseases
- Men with meiotic or chromosomal abnormalities on the sperm
- Advanced maternal age

Steps involved in PGD
- Embryo biopsy: one or two cells are removed from the embryo. The cell removal does not damage the embryos or affect its ability to continue to develop normally.
- Genetic study: when PGD is used to detect chromosomal abnormalities the genetic material of the sampled cell will be examined to check if the chromosomes analyzed have the right number of copies. When PGD is used to detect a monogenic hereditary disease the genetic material of the sampled cell will be examined for the presence or not of a gene mutation causing the hereditary disease.

To learn more...

Download