Fertility Blog

What is preimplantation genetic testing?

Depending on a woman’s age, the chance of getting pregnant with an IVF may be about 40%. Why isn’t it higher? Well, we think that the most likely reason women don’t get pregnant with IVF is that the embryo is not genetically normal, or it does not have the right number of chromosomes (this is called “aneuploidy”). The chance of this happening is also more likely as women get older, which is why the chance of having a baby is lower at higher ages.

Testing embryo’s for genetical deficiencies

What if you could test the embryo to know if it is genetically normal, before it gets transferred into the uterus? In fact, that can be done, and is called preimplantation genetic testing for aneuploidy (PGT-A). The idea is that if genetically normal embryos are transferred into the uterus, then the chance of having a baby goes up and the chance of miscarriage and not getting pregnant goes down. Some studies do show a benefit, in terms of a greater chance of having a baby.

Preimplantation Genetic Testing

To do the PGT-A, a couple needs to do IVF. The embryos are grown for 5-6 days, or until they are blastocysts. Then, the embryos are biopsied (have several cells taken from them). The cells are sent for genetic analysis and the embryos are frozen for future use. Once the results return, the patient will usually transfer one genetically normal embryo on a frozen cycle.

The benefits of PGT-A

The benefit of PGT-A, may be getting pregnant faster, with a lower chance of having a miscarriage. Also, only one embryo is transferred, so the chance of twins is lower. However, there are some possible down-sides to PGT-A. There is a small chance the test could be incorrect, there is added cost to the IVF cycle, the patient may have less embryos, and there may be a risk of damaging the embryos during biopsy. Although, PGT-A may be helpful for some patients, there are not big studies that show when and for which patients it is most beneficial. Having a conversation with your infertility doctor about PGT-A may help you understand if it is a good idea for you.

Brooke Rossi, MD