Carrier Screening and Preimplantation Genetic Testing (PGT) are key to evaluating which embryo to use for transfer. PGT is a cutting-edge procedure used to identify genetic abnormalities in embryos created with IVF. AFMC’s embryologists use state of the art technology for testing embryos in order to achieve high success rates.AFMC offers PGT to increase the chance of chance of a healthy pregnancy. PGT is a procedure in which embryos created during an IVF cycle are tested for genetic abnormalities prior to being transferred to the patient’s uterus. This helps our physicians choose the healthiest embryo for transfer.
PGS (“Preimplantation Genetic Screening”) and PGD (“Preimplantation Genetic Diagnosis”) both fall into the category of PGT (“Preimplantation Genetic Testing”). They each provide a way to test an embryo for genetic abnormalities prior to transferring it in hopes of it growing into a healthy baby. PGS is actually called PGT-A （Preimplantation Genetic Testing for Aneuploidies）
One of the most common reasons that an embryo transfer does not result in a pregnancy is due to abnormal embryo genetics. Carrier screening is a type of testing used to assess genetic risks to a patient/couple’s offspring that would not be evident just from personal or family history alone. The genetic conditions we look for through carrier screening are called recessive disorders, where both copies of the gene have to be no longer working properly in order for an individual to actually show symptoms of that condition.
In some cases, both members of a couple may be carriers for a recessive genetic condition such as cystic fibrosis or sickle cell anemia. Carrier screening also typically looks for common X-linked conditions, which are conditions that only females (individuals with two X chromosomes) carry such as Fragile X syndrome. It is completely normal to be a carrier; most people carry one or more recessive conditions and are asymptomatic. However, if a carrier has a child with someone who also carries the same condition, then there is a significant risk (25%) of having a child with that genetic disease.
If both members of a couple are found to be carriers of the same disease, or a female carrier for an X-linked disease, it is possible through in vitro fertilization (IVF) to screen embryos via pre-implantation genetic testing (PGT) and determine before pregnancy is attempted whether or not each embryo is predicted to be affected with the genetic disorder. Only embryos that are not affected with the condition are transferred back into the uterus to attempt pregnancy.
Even if a couple elects to undergo IVF without PGT, there are a few helpful considerations such as being aware that additional prenatal testing is indicated. In some cases, preparing a special pediatric care team to be ready after birth. Carrier screening is used to assess genetic risks that would not be evident from personal or family history alone. Carrier screenings look for recessive disorders, where both copies of the gene are no longer working properly in order for an individual to actually show symptoms of that condition.
PGT-A is an analysis of embryo cells to determine if there is the normal amount of chromosomes. An unequal division of either sperm or egg cells can result in an embryo having too few or too many chromosomes. Most people have 46 chromosomes because they inherit 23 chromosomes from each parent. If an embryo or a cell is missing a chromosome or has an extra one, it is called aneuploidy. Monosomy is a missing chromosome and trisomy is an extra chromosome. A child can only survive one type of monosomy, Turner syndrome, which is the absence of one of the X chromosomes. Trisomy of chromosome pairs can sometimes result in live birth, Down syndrome, also called trisomy 21 (an extra chromosome in normal pair # 21), Turner syndrome (trisomy 18) and Patau syndrome (trisomy 13). Down syndrome affects 1 in 700 babies, according to the Centers for Disease Control and Prevention. Aneuploidy is one of the greatest causes of failed implantation for pregnancy and miscarriage, as well as a major cause of birth defects in children.
Monogenic disorders are genetic disorders caused by pathogenic variants (or changes) in a single specific gene. Preimplantation Genetic Testing for Monogenic Conditions (PGT-M), formerly known as Preimplantation Genetic Diagnosis (PGD) is utilized in situations where there is already a known risk of a specific genetic disorder in the family. This knowledge can come from a known family or personal medical history, preconception/prenatal carrier screening, and/or previous genetic testing. The goal of PGT-M is to identify embryos that are free of the inherited condition for transfer. Preparing for PGT-M typically requires several months before a PGT lab is ready to analyze samples. This is because PGT-M involves the creation of a custom test for the family (sometimes referred to as a “probe”) that is tailored to the specific genetic variants(s) involved and other identifying genetic markers. PGT-A can be completed concurrently with PGT-M if desired by the patient or advised by a doctor. Performing PGT-M prior to embryo transfer can greatly reduce the risk of having a child with a specific genetic disorder.
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