a blog by Krystyn LaBate, Ph.D., July 22, 2013
Due to the fact that we lost four pregnancies (at that time), my husband and I decided to do genetic testing on the embryos from our second IVF cycle. This is referred to as Preimplantation Genetic Diagnosis (PGD). There are different types of PGD with the most common method referred to as FISH. FISH has the ability to look at 5-12 chromosomes within each embryo. This method is a good choice for someone that is looking for a specific disorder or an inherited disease. Since there are 23 unique chromosomes including one that determines gender, FISH is obviously not the choice for someone experiencing recurrent pregnancy loss as 11-18 chromosomes are left untested. Array-Comparative Genomic Hybridization (aCGH), an advanced form of PGD, has the ability to look at all 23 pairs of chromosomes in each cell obtained from an embryo. At the time that we did PGD there were just over 100 cases as it was a relatively new technology, not to mention, quite expensive. Despite my husband and I being genetically normal individuals determined by earlier karyoytyping, an abnormal number of chromosomes can result spontaneously from the maturation of the egg or during the process of embryo division. A common example of this is an extra chromosome number 21 (Down Syndrome or trisomy 21). It has been estimated that embryos fertilized in vitro contain chromosomal abnormalities in 50% or more of cases which leads to miscarriages.