Preimplantation genetic diagnosis (PGD)
What is PGD?
Preimplantation genetic diagnosis (PGD) is a reproductive technology used with an IVF cycle to increase the potential for a successful pregnancy and delivery. It is a genetic test on cells removed from embryos, to help select the best embryo(s) for pregnancy or to be free of a genetic disease.
What are the PGD steps during the IVF cycle?
After embryos are created in the laboratory, they are grown for five to six days. On day five and again on day six, the biopsy for PGD is done on all appropriately developing embryos. Biopsy involves removing a few cells from the trophectoderm, or the layer of cells that is ‘hatching out’ of the embryo at this stage of development. The embryos are stored while genetic material inside the removed cells is tested for abnormalities.
Is biopsy and PGD safe?
Yes. Data from many years of PGD in animals and thousands of live births in humans indicate that PGD does not lead to an increase in birth defects over that of the general population. In embryos where chromosomal microarray testing is performed, one can expect fewer pregnancies with chromosomal disorders since most chromosomal disorders are identified prior to transfer of the embryos to the uterus. Removal of a few of the cells of the early embryo does not alter the ability of that embryo to develop into a complete, normal pregnancy.
How are embryos chosen for transfer?
Embryos that have both a normal test result and appearance (morphology) can be transferred in a cryoembryo transfer (CET) cycle. While embryo morphology is helpful in selecting the best embryos for transfer, it is known that many embryos with significant chromosome abnormalities have normal morphology. Therefore, PGD results help to better identify the best embryos to transfer to the uterus. The combination of normal genetic testing with normal physical appearance indicates the highest chance of becoming a healthy pregnancy. All decisions regarding which embryo(s) to transfer to the uterus and how to use the remaining embryos are made together between the couple and our medical team.
Which tests are available in our clinic?
In our Clinic we perform the PGD of 24 chromosomes, testing for aneuploidies.
Which genetic disorders can be prevented by means of PGD?
Here we have listed a few examples of aneuploidies (and the corresponding genetic disorder) of certain chromosomes that can be prevented using PDG:
- Chromosome 13: Breast and ovarian cancers, deafness, Wilson Disease
- Chromosome 15: Marfan Syndrome, Tay-Sachs Disease
- Chromosome 16: Polycystic kidney disease, Alpha thalassemia
- Chromosome 17: Charcot-Marie-ToothDisease
- Chromosome 18: Niemann-Pick Disease, pancreatic cancer
- Chromosome 21: Down Syndrome
- Chromosome X: Duchenne muscular dystrophy (DMD), Turner’s Syndrome, and Fragile X Syndrome
- Chromosome Y: Acutemyeloidleukemia
Can the sex of the baby be selected with the help of PGD?
Yes. Even though the PGD test was not designed to allow for the selection of the sex of the future baby, it will give us useful information including the sex of every embryo created by IVF. It is therefore possible to determine beforehand which embryos will be implanted. The selection can be done together with the Intended Parents and so in the first attempts we can implant embryos of a certain sex according to the wish of the parents.