Our fertility and genetics experts at Columbia University Fertility Center are dedicated to give you personalized and highly advanced care in a sensitive and caring environment, and will help you make an informed decision about the possibility of reducing the risk of transmitting a genetic disorder.
In every cell in our body, we have 23 pairs of chromosomes. Chromosomes contain our genetic information- the blueprint for how our cells function – written in a four-letter code (“A”, “T”, “C”, and “G”). Having an extra or missing chromosome is called “aneuploidy.” Down syndrome is an example of an aneuploidy many people are familiar with is Down syndrome, where the individual is born with three copies of chromosome 21. An embryo with a chromosomal imbalance will either stop developing, result in miscarriage, or present with major birth defects. In addition to having the wrong number of chromosomes, there can be problems within the chromosomes themselves. For example, a change in one of the letters of the genetic code can result in a genetic disease such as Tay Sachs or cystic fibrosis, while having too many letters in a particular code can result in a disease like Huntington’s disease.
Pre-Implantation Genetic Testing for Aneuploidy (PGT-A)
With PGT-A, a complete chromosomal analysis of each embryo is conducted. The purpose of PGT-A is to select embryos with the highest implantation potential and reduce the emotional and physical trauma from a pregnancy loss or termination, or risk having a baby affected by an aneuploidy such as Turner’s syndrome or Down syndrome. PGT-A also helps reduce the number of embryos needed to achieve a successful pregnancy, thereby reducing the risk of higher order multiples such as triplets.
Pre-Implantation Genetic Testing for Monogenic Diseases (PGT-M)
PGT-M is the recommended test for couples who are at risk for inheriting a single gene mutation. The M stands for monogenic, meaning a disease resulting from a mutation in a single gene. This test can effectively identify embryos affected with a specific inheritable condition. Hundreds of inheritable conditions, many of which result in a short life expectancy or with limited treatment options, can be identified with PGT-M. Hereditary cancer genes (e.g. the BRCA breast and ovarian cancer mutations) can also be tested with PGT-M. PGT-M testing is usually conducted along with PGT-A so that we know that the embryo is free of the genetic disease for which the couple is at risk, as well as having the right number of chromosomes.
In addition to PGT-A and PGT-M, there are two additional variations of PGT, PGT-HLA (human leukocyte antigen) for matching for tissue donation and PGT- SR (structural rearrangements) for translocations.