​Preimplantation genetic diagnosis (PGD) allows couples undergoing in vitro fertilization (IVF) to screen their embryos for gender selection. This technology is also used to screen for a host of genetic diseases and disorders and is an ideal way of ensuring a healthy baby by  detecting problems before pregnancy has even begun.

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​How is PGD Done?
Preimplantation genetic diagnosis is used during an IVF cycle to identify specific embryos that carry abnormal genes. PGD can also be done to help select embryos of a particular sex, usually to avoid sex-specific diseases but it can also be done for family balancing. PGD is normally recommended for couples where one or both of the parents are a known carrier of a genetic disease like hemophilia or cystic fibrosis.

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PGD is usually performed after a woman’s eggs have been harvested and fertilized by her partner’s sperm but before the eggs have been transferred back to her uterus. When the fertilized egg has reached between the four and 10-cell development stage, one or two cells (known as blastomeres) are gently removed from each embryo using a microsurgery technique similar to that used in ICSI. The DNA from the removed blastomeres is then analyzed for any genetic diseases or disorders. If any are found, then those embryos are destroyed. Only those embryos with non-diseased genes will be transferred back to the mother.

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What Genetic Diseases Can PGD Test For?
Numerous diseases and disorders classified as either chromosomal disorders, single gene defects or sex-linked disorders can be tested for through PGD. Specific chromosomes are tested for specific disorders, including:

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• Chromosome 13: Breast and ovarian cancers, deafness, Wilson Disease

• Chromosome 15: Marfan Syndrome, Tay-Sach's Disease

• Chromosome 16: Polycystic kidney disease, Alpha thalassemia

• Chromosome 17: Charcot-Marie-Tooth Disease

• Chromosome 18: Niemann-Pick Disease, pancreatic cancer

• Chromosome 21: Down's Syndrome

• Chromosome X: Duchenne muscular dystrophy, Turner's Syndrome, Fragile X Syndrome

• Chromosome Y: Acute myeloid leukemia.

PGD can also benefit families where one child is sick and requires a stem cell transplant. Through PGD, a couple would be able to identify an embryo that would be a perfect match for their ailing child. Once the second child was born, stem cells from her umbilical cord would be collected and used for the transplant at no inconvenience to the child or mother, unlike bone marrow stem cells where collection is a painful and invasive procedure.

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