USC Fertility

How Does PGT-M (Formerly PGD) Work?

How does PGT-M work? Learn more about the process of PGT-M

Preimplantation genetic testing for monogenic disorders (PGT-M) can end the cycle of inheritable genetic disease. Formerly known as PGD, we can order this test as part of the IVF process. But how does PGT-M work? The test will involve the following steps for all couples.

  • Female partner takes medications to stimulate the ovaries to make multiple eggs grow
  • Fertility doctor retrieves the mature eggs with a transvaginal needle during an office procedure
  • Laboratory team combines the eggs and sperm using intracytoplasmic sperm injection (ICSI)
  • Embryos develop in the embryology laboratory over the course of 5-6 days

When the embryos have reached the blastocyst stage, we remove a few cells that would eventually become placenta from the outer layer of the embryo (a trophectoderm biopsy). Our team sends these cells to a special laboratory that will test for the specific abnormality in question using the most advanced techniques.

We then freeze the embryos immediately, using vitrification. When our clinic receives the results, we can thaw the normal embryos. The fertility doctor will then transfer one embryo to the uterus in a subsequent frozen embryo cycle. If we have additional unaffected and good-quality embryos, they can remain frozen for a future embryo transfer.

Answering other important questions about PGT-M

Aside from answering how does PGT-M work, there are still other important questions to answer.

Can you perform PGT-A at the same time as PGD? Yes. We can screen embryos for both chromosomal abnormalities and heritable genetic diseases or specific heritable chromosomal disorders.

When do you biopsy the embryo? Historically, laboratories biopsied embryos on Day 3 of their development when the embryo only contains 6-8 cells. Recent literature suggests that when then embryo can develop to the blastocyst stage at Day 5 or later when the embryo has 200 or more cells, the biopsy is safer. With Day 5 biopsies, we remove the cells from the outer layer of embryo which will eventually become the placenta, without harming the cells that will eventually become the baby.

Do I still need to have genetic testing during the pregnancy? Yes. PGT-M does not replace prenatal testing, such as cell-free fetal DNA testing, chorionic villus sampling (CVS) or amniocentesis. Though preimplantation genetic testing is highly accurate, patients should still have testing during pregnancy.

Is PGT-M safe? Thousands of clinical PGT-M cycles have been performed worldwide, resulting in the birth of hundreds of healthy babies. The procedure does not appear to affect the development of the embryo and subsequent pregnancy or the child once it is born. However, more follow up studies of children born after PGT-M are needed.

Contact us to learn more about this advanced type of genetic testing or to schedule an appointment. Our team is always happy to answer questions like, “How does PGT-M work?”