PGT-A, or Preimplantation Genetic Testing for Aneuploidy, is a genetic test performed during in-vitro fertilization (IVF) to screen embryos for chromosomal aneuploidy. Aneuploidy occurs when a cell fails to have two copies of each  chromosome, leading to birth defects, developmental abnormalities, or a non-viable fetus.

PGT can be performed with any IVF cycle and should be made only after careful discussion with a physician or genetic counselor.  PGT-A is an option in cases where multiple pregnancy miscarriages or unsuccessful IVF cycles have occurred, a history of pregnancies or children with chromosome abnormalities exists, and for aspiring parents who are older in age. Despite the apparent advantages of PGT, there remains some skepticism and controversy regarding its use. 

Embryos are monitored in the IVF laboratory until day 5 or 6, when they become blastocysts. A few cells are then biopsied (removed) from each embryo and shipped to the Gattaca Genomics genetic sequencing laboratory for PGT. Biopsied cells are expected to be genetically identical to the source embryo. Mosaicism, or cells genetically divergent from the source embryo, can be found in rare cases. Assuming that biopsied cells are genetically identical (monoclonal) to the embryo, average PGT results would make that embryo preferential for implantation.

The decision to have PGT must be made well before your IVF cycle.  If PGT is part of your IVF plan, your IVF lab will open a case with our laboratory.  For PGT-M, there is a test development phase during which our lab confirms if they can reliably detect the specific genetic condition in the patient’s embryo(s).  The test development phase can take 6-12 weeks after receiving all required DNA samples.  
This process must be fully completed before an IVF cycle (stimulation medications) will be started.

Chromosome abnormalities are common in embryos. Everyone has a chance to have embryos with chromosome abnormalities (aneuploidy). An individual’s risk for abnormal PGT-A results is most strongly influenced by the age of the person providing the eggs.

PGT-M or PGT-SR are options for many patients with a personal or family history of a specific genetic condition or chromosome rearrangement who wish to reduce significantly the chance of having a child affected by that condition. If you are interested in PGT-M or PGT-SR, the first step is for our genetic counselor and the genetic laboratory to review your genetic test results. The laboratory will determine if they can develop a test for your embryos to identify which ones are affected reliably.

No, but this is a widespread misconception. Embryos with average PGT results (of any type) can still fail to implant or result in a miscarriage. While many studies find the risk of miscarriage is lower in embryos with typical PGT-A results compared to untested sources, especially when the individual providing the eggs is 35 years or older, pregnancy losses can still occur. Normal PGT-A results mean the potential for the embryo to result in a successful pregnancy is high, but normal chromosomes are just one of many factors that contribute to the successful birth of a baby.

We strongly encourage all patients interested in PGT to have an appointment with genetic counselors.  This consultation will ensure you fully understand the risks, benefits, and limitations of this testing.  The genetic counselor will also determine if there are any additional concerns based on your personal and family history that should be addressed before your IVF.

Yes. There are four types of PGT:
1. Preimplantation genetic testing for aneuploidy (PGT-A): PGT-A screens embryos for the correct number of chromosomes. Human cells typically have 23 pairs of chromosomes (46 total) in each cell.  It is not uncommon in IVF for newly formed embryos to have chromosomal abnormalities. In most cases, these abnormalities happen as the result of the nuances of the laboratory environment as opposed to being inherited from the parents.  Examples of aneuploidy include Down syndrome and Turner syndrome. 
2. Preimplantation genetic testing for monogenic disorders (PGT-M): PGT-M screens for genetic diseases in the embryo affecting a single gene and is used when one or both parents are known carriers of the gene.  
3. Preimplantation genetic testing for polygenic disorders (PGT-P): PGT-P screens for a wide range of disease-associated genes. Examples of diseases that PGT-P can identify include heart disease, coronary artery disease, hypertension, type 2 diabetes, obesity, many cancers (i.e. breast cancer and colorectal cancer), psychiatric disorders (i.e. depression, schizophrenia and anxiety) and neurological disorders (i.e. Alzheimer’s disease, metabolic disorders,  nutritional disorders (i.e. food sensitivities), and autoimmune disorders (i.e.  rheumatoid arthritis, lupus). PGT-P can even predict genetic predisposition for traits such as physical attributes (such as height) or mental aptitude. 
4. Preimplantation genetic testing for structural rearrangements (PGT-SR): PGT is screens for chromosomal rearrangements such as a translocation (the relocation of a portion of one chromosome to another) or inversion (the flipping a region of a chromosome).  Translocations and inversions increase the risk of miscarriage, stillbirth, and serious health issues. 

Yes. PGT-A screens for chromosome abnormalities that can occur randomly in any individual’s embryos. Chromosome abnormalities are common in embryos and are not usually inherited. Therefore, we do not expect patients to have a family history of any chromosome conditions. The main risk factor is the age of the person contributing the eggs.

Yes. While chromosome abnormalities can happen in any embryo or pregnancy, the chance for missing or extra chromosomes (aneuploidy) does increase with the age of the person providing the egg(s). 
Please remember these are averages so you may have more or less embryos with abnormal PGT-A results than expected based on age.  In some IVF cycles, a patient may not have any embryos with normal PGT-A results to transfer.  It is also important to keep in mind that the number of embryos an individual will have available to test also tends to decrease with the age of the person providing the eggs.

Embryos with aneuploidy are more likely to result in a failed transfer or miscarriage, PGT-A results may increase the chances of a successful pregnancy by providing an informed selection of embryos that are typically randomlyselected. 
PGT-A can also mitigate chromosomal aneuploidies such as Down syndrome (trisomy 13), Turner syndrome (missing X chromosome), Klinefelter syndrome (extra X chromosome), Edward Syndrome (trisomy 18), and Patau Syndrome (trisomy 13).  
It should be noted that study outcomes remain inconclusive regarding whether the use of PGT-A statistically reduces a patient’s miscarriage risk. Characteristics of the individual patient, such as age and family history, make outcomes multifactorial. If you want to learn more about PGT-A, we recommend you discuss this test with your physician and our genetic counselor.  Genetic counselors can review your circumstances to help you determine if PGT-A is right for you.

An embryo with average PGT-A results is predicted to have the correct number of chromosomes and no evidence of large chromosome deletions or duplications.  PGT-A cannot detect all chromosome abnormalities, such as small extra or missing pieces of chromosomes (microdeletions and microduplications).  PGT-A cannot detect single-gene disorders.  Average PGT-A results cannot rule out the possibility a child may be born with a birth defect, autism, developmental delay/intellectual disability, or severe health issues not caused by detectable chromosome abnormalities. 
Average PGT-A results cannot guarantee a successful transfer or prevent miscarriage. Abnormal PGT-A results may refer to an embryo with either aneuploid or mosaic results.  
Aneuploid means the embryo is detected to have a more or less than the normal two copies of each chromosome.  Most embryos with aneuploid PGT-A results are not recommended for transfer because they have a very low likelihood of resulting in a successful pregnancy.  Embryos with mosaic results are complex but may be considered for transfer..

An embryo with normal PGT-M results is predicted to be free of the genetic condition for which it was tested.  For autosomal recessive conditions, PGT-M will also identify whether the unaffected embryo is a carrier.  Since carriers of autosomal recessive conditions are not expected to have symptoms, those embryos may be transferred if the patient wishes.  Abnormal PGT-M results mean the embryo is expected to be affected with the condition for which it was tested.  Therefore, those embryos are typically not recommended for transfer. An embryo with normal PGT-SR results is predicted to have the correct number of chromosomes without deletions or insertions of chromosomal fragments.  The laboratory will examine the chromosomes involved in the translocation or inversion.