Genetic testing in IVF serves as one of the most advanced methods of increasing the likelihood of a healthy pregnancy inn individuals. Many couples are confused on PGD vs PGS tests in this regard.
While both Preimplantation Genetic Diagnosis (PGD) and Preimplantation Genetic Screening (PGS) are geared towards embryo screening and testing before implantation occurs, each of them serves a distinctive purpose. Let’s understand together what they are and how they work, as well as what are the scenarios under which they are recommended
Introduction to Genetic Testing in IVF
Genetic testing in IVF is done right before transferring the embryo to the uterus to check out their current health status. This helps in early identification of any chromosomal issues that might lead to health problems in the baby, as well as distressing situations such as a miscarriage or a failed implantation.
In this regard, for couples, embryo screening plays a crucial role, especially for those who have observed failed IVF cycles, have a past history of genetic disorders, or have had cases of miscarriage. Genetic testing in IVF has different types, such as PGD (now called PGT-M) and PGS (now referred to as PGT-A). Although these terms might sound similar, both of them play quite different roles throughout the IVF process.
What is PGD and How Does it Work?
PGD or Preimplantation Genetic Diagnosis is a type of genetic test conducted on an embryo to find out certain inherited diseases and underlying conditions. It is particularly helpful where either or both parents are carriers of known genetic defects like cystic fibrosis, thalassemia, sickle cell anaemia, or Tay-Sachs disease.
PGD is now commonly known as PGT-M (Preimplantation Genetic Testing of Monogenic or single-gene diseases). It starts with IVF, in which embryos are formed in a laboratory. A couple of cells are taken off each embryo on the fifth or sixth day of development, at the blastocyst stage. The cells are then examined in the laboratory to check whether or not the desired genetic condition is present in it. The embryos which are not affected by the disorder are only transferred into the uterus. The method significantly minimizes the chances of passing genetic diseases to the child.
What is PGS and how is it Different?
PGD is applied to detect certain inherited diseases, whereas PGS is applied to screen for general chromosome issues.
PGS or Preimplantation Genetic Screening is a test that is not specified for finding out hereditary diseases, but rather examines whether an embryo has the right number of chromosomes or not. This test is considered quite effective and is now known as PGT-A (Preimplantation Genetic Testing for Aneuploidy). Usually, the human body possesses 46 chromosomes, which are organized in pairs of 23.
Excessive or insufficient chromosomes in an embryo, known as aneuploidy, may result in a failure to implant in the uterus or result in miscarriage or birth defects such as Down syndrome. PGS allows embryo selection with the right number of chromosomes, which makes the selection of the healthiest ones by doctors much easier. This boosts the possibility of a successful pregnancy as well.
Indications for PGD and PGS
Use PGS/PGT-A in the cases when your age is above 35, you have continuously faced IVF failures or multiple miscarriages, you are already going through IVF with donor eggs, or you want to mitigate the risk of chromosomal abnormalities. Also, there might be some cases where the fertility specialist may recommend you both PGD and PGS if there is a need for both chromosomal testing as well as checking single-gene conditions.
Benefits and Limitations
In case you are wondering which one to choose between PGD vs PGS in IVF, this totally depends on your fertility background, age, and medical history. However, you can check for a few symptoms. Use PGD/ PGT-M when you already have a child with a specific genetic condition, you as a partner are carriers of a known genetic disorder, or you have a family history of the hereditary disease.
PGD vs PGS are both types of genetic testing in IVF and they present numerous significant advantages; Among the greatest benefits is the increased likelihood of a healthy pregnancy. The chances of success are higher by screening embryos that are not affected by genetic or chromosomal abnormalities. This testing also aids in alleviating the risk of miscarriage and serve the best to females who are over the age of 35 years or those who have had lost pregnancies in the past.
The second major benefit is that it enables couples to make more informed choices in the course of their IVF process because they have more definite information regarding the well-being of their embryos. PGS in some cases may also indicate the sex of the embryo, which can be helpful in preventing sex-linked diseases or family balancing in some cases.
There are a few limitations of these tests as well. Though both of them are quite accurate, but this does not mean that a baby will be born with no genetic conditions, and there are still other conditions that are not detectable with this type of testing. Moreover, genetic testing is an extra expense to an already costly process of IVF. It also has a slight chance of damaging the embryo in the process of conducting a biopsy, where the cells are taken out of the embryo to test them.
In addition, there are those who find it morally questionable to choose an embryo trait beyond medical necessities. In spite of these constraints, genetic testing using PGD or PGS is a source of relief to many couples and enhances their likelihood of becoming parents.
Cost and Success Rate Considerations
Genetic testing such as PGD vs PGS, may increase the cost of IVF in addition to the normal cost of IVF. Nevertheless, a considerable number of couples consider that it is worth it. These tests have the ability to raise the possibility of successful implantation and a healthy birth. They also prevent the stress and expense of unsuccessful IVF treatments and reduce the chances of miscarriages or genetic abnormalities.
The success rates are slightly variable but most of the clinics have higher results, particularly in older women or women who have previously had failures with IVF. The rule of thumb is to always consult a fertility doctor to find out what suits your case.
Final Recommendations
Understanding the contrasting differences between PGS vs PGD holds immense value when you are going through the procedure of IVF and are highly concerned about the genetic health of your baby. PGD (PGT-M) is the apt test in case you or your partner are likely to transmit a certain illness to the child. Whereas, PGS (PGT-A) can enhance your chances of pregnancy if you are beyond 35 years of age or when you have unsuccessful IVF cycles or miscarriages.
These tests cannot guarantee a child, but they fully assist in selecting the healthiest embryos for the transfer. At the end, you are advised to never hide anything from your doctor to get the best recommendations for a healthy pregnancy.