Embryo Testing: The Difference Between PGT-A and PGT-M

Jennifer "Jay" Palumbo

IVF mom of two and infertility advocate

If you’ve been doing your homework about various forms of fertility treatment as well as the reproductive technology available, you may have seen the acronyms PGT-A and PGT-M.

In order to understand what they mean, we need to first explore two other acronyms: IVF and FET. FET stands for Frozen Embryo Transfer, and it may be recommended as the best course of action to you conceiving.

FET varies slightly from your typical in vitro fertilization (IVF) protocol, and for some, it may be particularly beneficial for their specific diagnosis as it provides the option of genetic testing.

In this article, we’re going to review what the difference is between a fresh IVF cycle and FET, the difference between PGT-A and PGT-M and the advantages both can have.

How Is a Frozen Embryo Transfer Timeline Different than Fresh?

In Vitro Fertilization (IVF) is a technique where a woman’s eggs and man’s sperm are combined with a woman or donor’s eggs to create an embryo or embryos. An embryo(s) is transferred to the intended mother or a gestational carrier’s uterus through her cervix to enhance the chances of pregnancy within days of fertilization.

When you go through a fresh in vitro fertilization cycle, you take hormone medications for approximately two weeks to produce eggs, and have regular doctor appointments to see when the eggs are ready to be retrieved. Once you get the go-ahead from your fertility doctor, the eggs are fertilized with your husband, partner, or donor’s sperm.

The way a frozen embryo transfer timeline is different is those two weeks leading up to the retrieval are removed from the equation as you’ve done all the preparation previously. This makes the frozen embryo transfer timeline shorter. When you’re doing a FET cycle, you are just transferring the embryo(s), which will entail one day.

Advantages of Frozen Embryo Transfer Timeline and Genetic Testing

Thanks to the advancement in freezing technology known as vitrification, FET has become possible. This is rapid freezing in liquid nitrogen. Vitrification prevents the formation of ice crystals on the embryo. This makes freezing or unfreezing the embryos possible with minimal to no damage.

Another advantage is some fertility doctor’s belief that when you immediately freeze the embryos after going through the IVF stimulating process, it gives the intended mother’s body time to return to its typical environment before transferring any embryos.

However, one of the biggest assets to doing a Frozen Embryo Transfer is you have the option to have genetic testing done. There is Preimplantation Genetic Testing for aneuploidy (PGT-A, formerly known as PGS) and Preimplantation Genetic Testing for monogenic disease (PGT-M, formerly known as PGD).

If you’ve had a series of miscarriages or are a woman over a certain age, it means you have a greater risk for chromosomal abnormalities. PGT-A looks at your embryos to screen that they are, in fact, the correct number of chromosomes. If the embryos do not have the correct number, the embryos are called “aneuploid”, hence the ‘A’ in PGT-A.

Knowing which embryos are considered chromosomally healthy will help determine which embryo(s) to transfer. Euploid embryos, which is when the embryos have the correct number of chromosomes, have a higher rate of implantation in the uterine lining and a lower chance of miscarriage.

PGT-M is for those who have a disease that puts them at an increased risk of passing the condition onto their offspring. Pre-implantation Genetic Testing for Monogenic Diseases (PGT-M) screens your embryos of the condition you or your partner is a carrier of. So, for example, if you are a carrier of cystic fibrosis, muscular dystrophy, or sickle cell anemia, PGT-M can determine which of the embryos are unaffected, so that only those would be chosen for transfer.

Whether you pursue FET or genetic testing, is something to determine with your doctor. If your history includes recurrent pregnancy loss, a family history of a genetic condition, if you’ve had previous failed IVF cycles, etc. – these are all factors to share with your reproductive endocrinologist as you have this conversation. That way, you can work out what are the next best options for future fertility treatment.

Please know that as you explore every option, GoStork is here to provide resources, blogs, and options to support you along the way!