Assisted Reproductive Technologies (ART) including In Vitro Fertilization (IVF)
The IVF process can be broken down into 5 general steps:
Intra-Cytoplasmic Sperm Injection (ICSI)
Pre-Implantation Genetic Diagnosis (PGD)
PGD or Pre-implantation Genetic Diagnosis, a relatively old technology that has recently increased in popularity. PGD can test for either a specific gene abnormality such as Tay Sachs or Cystic Fibrosis, or it can test for an irregular arrangement in the normal chromosome count, known as aneuploidy. Normally our genetic material is arranged on chromosomes. We each have 23 pairs of chromosomes. When we are conceived, each of the two cells, the sperm and egg, contributes a single set of chromosomes. When the sperm penetrates the egg, the job of the egg is to bring these chromosomes together to create 23 pairs. As we get older, the architecture inside the egg gets older and is not as proficient in bringing these two sets together as when it was younger, so there is an increased chance of having an irregular number of chromosomes in the developing embryo. (SEE CHART)
We call this irregular number of chromosomes Aneuploidy. Down’s Syndrome is the most famous form of aneuploidy, when there is a normal compliment of chromosomes, or 23 pairs, plus an additional number 21 chromosome, resulting in “trisomy,” or three sets of Chromosome 21. PGD testing can test for 9 to 12 of the most common forms of aneuploidy, reducing the chances for aneuploidy by up to 90%.
PGD is usually performed on the third day after egg retrieval. At this stage, there are usually between 4 and 8 cells in the developing embryo. Our embryologist delicately removes one cell from each of the developing embryos,
which is fixed to a slide and sent via courier to our affiliate Reprogenetics, the most experienced cytogenetics laboratory in the world. At Reprogenentics, the cells are stained for the 9 most common chromosome abnormalities, which make up 90 % of aneuploidies. Not all of the chromosomes are tested.
This is an example of the staining technique called FISH, or Florescent In Situ Hybridization, which allows us to determine which embryo has an irregular number of the tested chromosomes.
That information is relayed back to us and the good embryos are then used for embryo transfer.
Stillbirth, the number one cause of infant deaths in the U.S. has genetic implications. (2001, Data from National Center for Health Statistics, CDC). 7% of stillbirths and neonatal deaths have chromosomal abnormalities. (Patients Fact Sheet, Genetic Screening for Birth Defects, ASRM 2002).
Recurrent miscarriages and repetitive failed IVF may be due to genetic abnormalities. Preimplantation genetic diagnosis (PGD) can be used as a diagnostic procedure to identify embryos that carry genes for certain diseases.
According to a report from the American Society of Reproductive Medicine (ASRM), “The advantage of accurately diagnosing these genetic abnormalities in the embryo obviates the 25% to 50% risk of transferring an affected embryo with the specific abnormality in question.” (A Practice Committee Report: Preimplantation Genetic Diagnosis, ASRM. June 2001).