Preimplantation Genetic Testing (PGT)
The term PGT is often used as a catch all phrase for genetic testing of an embryo which can be performed before it is placed back into the uterus. There are in fact two distinct types of genetic analysis which can be performed on preimplantation embryos. In both methods, a sample of the embryo is obtained and the sample is sent to a genetics laboratory which specializes in this type of testing while the embryo remains in culture in the embryology laboratory. The results are returned usually within a 24 hour period which allows the physician, patient and embryologist to select which embryos to transfer back to the uterus. Families affected by essentially any inherited disease can reduce the risk their offspring will suffer that genetic disorder.
The first type, preimplantation genetic diagnosis (PGD) tests for a specific disease, usually a genetic mutation, which the patient may already know is in their family history. Because a thorough genetic screening is completed on all patients prior to treatment, occasionally a risk of disease transmission is only discovered during infertility treatment. Usually bloodwork from both the male and female partner (and any affected offspring) are sent to the genetics laboratory in advance to begin the process of designing an appropriate test for that family. This does require some advanced planning.
The second type, preimplantation genetic screening (PGS) tests for chromosomal anomalies in the preimplantation embryos. Human cells have 46 chromosomes (23 were donated by the egg and 23 by the sperm). If there is an extra copy, or a missing copy, this will severely inhibit the embryos ability to develop to a healthy term baby. There are many other types of chromosomal anomalies, most of which PGS can screen for. Certain patients are at an increased risk for these anomalies, for example women over the age of 36 or women who have experienced multiple miscarriages. This type of testing is standard across the board and can be set up rather quickly with very little advanced planning.
In some cases a patient may be at serious risk of conceiving a baby which is affected by both a chromosomal anomaly as well as a specific genetic disease. In these cases it is usually possible to test for both problems at the same time.
Most often we work with the leading genetic laboratories Genesis Genetics and Reprogenetics to offer PGD as an option to couples who are at risk of having a child with an inherited disorder, although we can work with any genetics laboratory that specializes in this type of testing. The biopsied cells are analyzed to determine which embryos have inherited the disease and which embryos are free of the disease. These results are discussed with the patient and a decision is made to determine the number of disease free embryos to transfer.
Preimplantation Genetic Testing Study
RSofNY is conducting a research study with Stony Brook University and The New School. This is a voluntary study for women and men who are thinking about, have chosen to do, or have chosen not to do preimplantation genetic testing within the past 6 months. The study is anonymous and online. The purpose of this study is to investigate considerations, concerns, and factors underlying the decision-making process about whether to use PGT testing. Visit here to learn more!