Preimplantation Genetic Testing, or PGT, has become more frequent in recent years with patients undergoing IVF. Nearly half of all patients request PGT as a way to uncover potential risks for birth defects as well as embryo viability.
Whether you have a known genetic condition in your family, or you simply want to ensure a healthy pregnancy and delivery, PGT is one of the most useful tools available. Although the test itself has been around for more than 30 years, it really only became mainstream in the last 10 years. It is especially helpful in determining the health of the embryo in mothers of advanced maternal age (over age 35) when the risk of chromosomal complications is greater.
If you’re interested in PGT, you likely have some questions. We’re here to clear up any confusion about the process and explain what the test is intended to uncover. If there are concerns that aren’t addressed here, please feel free to ask a member of our team.
Types of PGT
Currently, there are three specific types of PGT available together with IVF:
- PGT-A tests embryos for aneuploidies, genetic disorders resulting from an abnormal amount of chromosomes. A healthy embryo has 46 chromosomes; 23 from each biological parent. An extra chromosome (47) indicates trisomy and a missing chromosome (45) indicates monosomy. One of the most common trisomy chromosomal defects is Down syndrome, with Turner syndrome an example of a monosomy defect. Both involve developmental delays and some physical issues and vary in severity. Also, embryos with more or less than the correct number of chromosomes may result in miscarriage or a failed IVF cycle.
- PGT-M is performed when one or both biological parents have a known genetic condition or abnormality. The M stands for monogenic, or a single gene disorder such as Sickle cell anemia, Huntington’s disease, Cystic fibrosis or Duchenne muscular dystrophy.
- PGT-SR formerly known as PGD (preimplantation genetic diagnosis), tests for structural rearrangement of the chromosomes. This results in deletion, relocation, inversions and other issues involving abnormal placement of chromosomes. The condition could result in miscarriage, stillbirth or birth defects.
PGT with IVF is the only genetic screening test available before pregnancy. Your doctor can perform all other tests after conception. PGT-A is the most popular and common of these tests, with your doctor recommending the other tests only in certain circumstances.
How PGT Works to Help IVF Success
There are two main obstacles standing in the way of a successful IVF cycle: failed embryo transfer and miscarriage. PGT helps increase your odds for success by confirming the health of the embryo. A healthy embryo has a better chance of implanting in the uterus and thriving, resulting in a healthy delivery.
Once egg retrieval and fertilization occur and the embryo grows to a sufficient number of cells (around day five or six, the blastocyst stage), the lab removes a few cells (this in no way harms the developing embryo) to test the chromosomal makeup. The cells (not the embryo) are then sent to a genetics lab for embryo biopsy testing, or PGT.
The reason doctors wait to perform the embryo biopsy until the blastocyst stage on day five or six following fertilization is because, at that point, two very distinct groups of cells become apparent: the cells that develop into the fetus and the cells that make up the placenta. The lab removes only the pre-placental cells leaving the cells that develop into the baby intact.
Removal of the pre-placental cells in no way harms the developing embryo, nor does it interfere with implantation in the uterus. In fact, a recent study showed no difference in the implantation rates for PGT embryos versus non-tested embryos. In most cases, you’ll receive PGT results within three weeks after testing.
Just How Accurate is PGT?
The accuracy of PGT test results for aneuploidies is high, around 98 percent. However, in a study reported by the American Society for Reproductive Medicine (ASRM), the results of PGT-A on those undergoing their first ever IVF cycle found a 0 percent clinical error rate. That means the PGT test results were highly accurate in determining which embryos would result in a successful pregnancy.
What do PGT Test Results Mean?
There are a few different things you can learn from PGT about your embryos and your odds for a successful IVF pregnancy, including which embryos are normal and viable, which embryos, if any, carry a chromosomal defect, and the sex of the embryos.
Using the results of your PGT, you can select the embryo with the highest chance for a successful pregnancy that results in a live birth. But remember, the PGT assessment doesn’t guarantee success. Other things, like maternal age, also factor into the success of your IVF cycle.
Another recent study by the ASRM estimates the success rate for implantation of a PGT-declared normal embryo (one that shows no chromosomal abnormalities) is around 60 percent. That means you have increased odds of carrying a pregnancy to term that results in a live birth when you use PGT for identifying healthy embryos.
PGT is a Personal Choice
Of course, choosing whether or not to go through PGT is entirely personal. You and your partner will want to discuss the benefits with your fertility specialist and make an educated decision together.
There are advantages and disadvantages to the testing, including the added expense of the test. But for those who are concerned about the risks of chromosomal abnormalities due to age, have experienced recurrent miscarriage or have a known genetic predisposition, the information you get from PGT is invaluable.
Here to Answer Your Questions
For more information on PGT for IVF, contact Rise Fertility today. Our compassionate and caring team wants to work with you in achieving your goal of growing a healthy family. Please contact our office today and schedule a consultation.
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