Preimplantation Genetic Testing – FAQ

Preimplantation genetic testing (PGT) is a procedure used to identify genetic differences in embryos created with in vitro fertilization (IVF). PGT is performed before embryos are transferred to the uterus. The goal of PGT is to significantly reduce the chances of transferring an embryo with a specific genetic condition or certain types of chromosome abnormalities.

Yes. There are three types of PGT:

• Preimplantation genetic testing for aneuploidy (PGT-A): This type of PGT screens embryos for certain chromosome abnormalities. Human embryos typically have 23 pairs of chromosomes (46 total) in each cell. One chromosome in each pair is contributed by the egg, and the other is contributed by the sperm. It is common for embryos to have random chromosome abnormalities, which is called aneuploidy. In most cases, these chromosome abnormalities happen by chance and are not inherited from a parent or donor. Embryos with aneuploidy are more likely to result in miscarriage or a failed transfer. Some types of aneuploidy may result in the birth of a baby with a chromosome condition such as Down syndrome or Turner syndrome.
• Preimplantation genetic testing for monogenic disorders (PGT-M): This type of PGT is performed when a patient has an increased risk for a specific genetic condition to occur in their embryos. PGT-M is used when an individual is affected with a genetic condition that could be passed to their children, for individuals who are carriers for an X-linked condition, or when an individual and their partner or donor are carriers for the same autosomal recessive condition.
• Preimplantation genetic testing for structural rearrangements (PGT-SR): This type of PGT is performed when a patient or their partner has a rearrangement of their own chromosomes such as a translocation or inversion. A person with a translocation or inversion is at increased risk to produce embryos with chromosome abnormalities (aneuploidy), which can result in failed transfers, miscarriage, stillbirth, or a child with serious health issues.

PGT-A is not a standard part of IVF – it is considered an “add-on.” There remains ongoing debate about which patients might benefit from the use of PGT-A (see questions 20 and 21). PGT-A is a tool that helps patients and providers better rank the available embryos for transfer. Ultimately, the decision to add on this testing to an IVF cycle is complex and should be made after careful discussion with your physician in coordination with a genetic counselor experienced in PGT-A. PGT-A is most often considered for patients who have had recurrent pregnancy losses (miscarriages), multiple unsuccessful IVF cycles or transfers, a prior pregnancy or child with certain chromosome abnormalities, or based on the age of the individual providing the eggs.

By contrast, PGT-M and PGT-SR are only performed when the patient, their partner, and/or their donor have abnormal genetic test results that put the embryos at increased risk for a genetic disorder or specific chromosome abnormalities that increase the risk of miscarriage. PGT-M is an option for patients with an increased risk for a single-gene disorder in their embryos, such as cystic fibrosis or sickle cell anemia. PGT-SR is an option for patients who have a chromosome translocation or inversion that results in a higher rate of pregnancy loss (miscarriage). PGT-M and PGT-SR allow patients the opportunity to reduce the risk of having an affected child or miscarriage, respectively, prior to becoming pregnant.

All three types of PGT are performed in a similar way. The patient goes through their IVF cycle and egg retrieval as recommended by their physician. The embryo(s) are cultured in our lab until days 5, 6, and 7 when they are expected to reach the blastocyst stage. At that time, a small number of cells are removed from each eligible embryo and

shipped to an outside lab for PGT. The cells are taken from a part of the blastocyst that will eventually form the placenta and supporting structures. These cells are assumed to be representative of the rest of the embryo; however, this may not always be the case due to circumstances such as mosaicism (see question 16). The embryo(s) must be frozen while PGT is performed. Based on the PGT results, an embryo can be selected, thawed ,and transferred to the uterus of the patient or their gestational carrier at a later date.

In addition to the biopsied cells from the embryo(s), other DNA samples may be required for PGT. Some versions of PGT-A and PGT-SR may require DNA samples from the patient and their partner or donor, which must be collected prior to the egg retrieval.

For PGT-M, the required samples vary. The lab performing PGT-M will evaluate your unique case and determine what samples are needed to develop testing for your embryo(s). PGT-M will always require DNA samples (typically blood) from the individuals contributing their eggs or sperm. DNA samples from other family members may also be requested on a case-by-case basis. In some cases, a sperm sample may also need to be provided. Please see question 6 if you are using a non-directed (“anonymous”) egg or sperm donor.

For PGT-A and PGT-SR, we have options that do not require DNA samples from the sperm or egg donor. For PGT-M, each case is unique and must be reviewed by a genetic counselor. For individuals using a sperm donor, PGT-M may be possible but requires the purchase of an additional vial of sperm. In some cases, it may not be possible for the lab to develop reliable testing for embryos created using a non-directed donor, especially if a DNA sample from that donor is not available. This is a common obstacle with non-directed egg donors.

Yes. The biopsy process, which removes cells from each embryo for PGT, has a small chance of damaging the embryo. Additionally, since the embryo(s) must be frozen while PGT is performed, they must also undergo a thawing procedure prior to transfer. In our center’s experience, the survival rate of embryos that were biopsied and later thawed for transfer is approximately 97%.

The decision to have PGT needs to be made well in advance of your IVF cycle. If PGT is part of your IVF plan, you will be scheduled for a genetic counseling appointment. Our office will open a case with the PGT lab and additional consent forms may be required. Additionally, DNA samples from the patient, their partner or donor, and sometimes other family members may need to be collected in advance of the IVF cycle (see question 5).

For PGT-M, there is a test development phase during which the lab confirms if they will be able to reliably detect the specific genetic condition in the patient’s embryo(s). The test development phase can take 6-12 weeks after all required DNA samples are received. Typically this process must be fully completed before an IVF cycle will be scheduled.

All patients who intend to do PGT are required to have an appointment with our genetic counselor. 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 prior to your IVF cycle.

PGT-A is primarily designed to ensure an embryo has the correct number of chromosomes. PGT-A screens embryos for whole missing chromosomes (monosomies) and whole extra chromosomes (trisomies); these are referred to as whole chromosome aneuploidies. PGT-A also screens for missing or extra pieces of chromosomes (deletions or duplications, respectively) above a specified size; these are referred to as segmental aneuploidies. Some, but not all, versions of PGT-A may detect additional types of chromosome abnormalities such as triploidy, mosaicism, and uniparental disomy (UPD). An embryo without any detectable chromosome abnormalities is referred to as euploid. Our genetic counselor will review the types of results that can be detected at your appointment.

Yes. PGT-A screens for chromosome abnormalities that can occur randomly in any embryo. 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 (see question 13). PGT-A does not replace routine prenatal screening. Even if a euploid (normal) embryo is transferred into the uterus and pregnancy results, it is recommended the patient be offered routine prenatal testing as indicated by their OBGYN. (see questions 28 and 29).

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 at the time of their retrieval (see question 13).

Yes. While chromosome abnormalities can happen in any embryo or pregnancy, the chance for missing or extra chromosomes (whole chromosome aneuploidy) does increase with the age of the person providing the egg(s). The lab we use most often reports the following chances for whole chromosome aneuploidy: 17% for individuals under 35 years old, 30% for individuals 35-37 years old, 49% for individuals 38-40 years old, 68% for individuals 41-42 years old, and 80% for individuals who are 43 years or older at the time of egg retrieval.

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 that are eligible for transfer.

An embryo with normal (euploid) PGT-A results is predicted to have the correct number of chromosomes and no evidence of large chromosome deletions or duplications (see question 10). Embryos with normal PGT-A results are predicted to have the highest potential of resulting in a successful pregnancy. However, normal PGT-A results cannot guarantee a successful transfer or prevent miscarriage (see question 27). PGT-A cannot detect all chromosome abnormalities, such as small extra or missing pieces of chromosomes (microdeletions and microduplications). PGT-A cannot detect any single- gene disorders. Normal PGT-A results cannot rule out the possibility a child may be born with physical or developmental health issues (see question 30).

Abnormal PGT-A results may refer to an embryo with either mosaic or aneuploid results. Embryos with mosaic results have the potential to result in successful pregnancies and are eligible for transfer at our clinic if a patient has no embryos with euploid (normal) results available (see questions 16 and 17). Aneuploid means the embryo is predicted to have a chromosome abnormality present in all of the tested cells. 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. However, our clinic does offer patients the option to transfer embryos with non-mosaic segmental aneuploid results in certain circumstances (see question 18 and 19).

Yes, your PGT-A results will include the predicted sex of each embryo based on the embryo’s sex chromosomes. Embryos with XX chromosomes are predicted to be female, while embryos with XY chromosomes are predicted to be male. While the sex chromosomes are typically an accurate predictor of biological sex, they are not the only factors involved in sex development and are therefore not a guarantee of a particular sex. When our genetic counselor calls with your results, you will be asked whether you would like to know the predicted sex of your embryo(s) or have it kept a surprise. While this information may be used to request the transfer of a specific embryo if a patient prefers one sex, this option may not be available in every situation. Our genetic counselor will review the clinic’s sex selection policy with you prior to your IVF cycle.

Mosaicism refers to a mixture of two or more types of cells within the same embryo. Most often it refers to an embryo with some cells that are chromosomally normal (euploid) and some cells that are chromosomally abnormal (aneuploid). On days 5/6/7, an embryo is made up of approximately 100-200 cells. Our embryologists will remove five to 10 of these cells for PGT. In most cases, we expect all of the embryo’s cells to be identical so testing this small sample will give us accurate information about the whole embryo. However, if the embryo has mosaicism, the 5-10 cells which are biopsied may not accurately represent all of the cells of the embryo. For instance, the biopsied cells may be chromosomally normal, but other untested cells within the embryo are abnormal. Conversely, the 5-10 biopsied cells may be chromosomally abnormal, but other cells within the embryo are normal. This can result in false negative or false positive results, respectively. If the 5-10 biopsied cells contain a mix of chromosomally normal and abnormal cells, a mosaic result may be reported by the PGT lab. The detection and reporting of mosaic results varies by lab, and our genetic counselor will review the specifics with you.

Our clinic will transfer embryos with mosaic PGT-A results if a patient wishes to do so. We require the use of any embryos with chromosomally normal (euploid) results first. Additionally, we require a genetic counseling appointment to review your embryo’s mosaic results as well as our current understanding of the risks and benefits of transfer. The decision to transfer an embryo with mosaic results is complex, and our understanding of these embryos is still evolving. While some studies have found a higher risk for miscarriage and a lower live birth rate when transferring embryos with a mosaic result compared to a euploid result, there have been many successful live births published. Data about long-term outcomes for children born after the transfer of embryos with mosaic results is still lacking. Before proceeding with the transfer of an embryo with a mosaic PGT-A result, the patient and their partner (if applicable) will also be required to sign a waiver acknowledging they have been counseled about the risks and benefits.

If a patient does not wish to transfer an embryo with mosaic PGT-A results, they may choose to continue to cryopreserve the embryo for potential use in the future, discard the embryo, or donate the embryo for research.

Non-mosaic segmental aneuploidy is a type of abnormal PGT-A result. Non-mosaic means the abnormality is predicted to be present in all the tested cells. Segmental aneuploidy means the abnormality detected is one or more partial chromosome deletions or duplications. Unlike whole chromosome aneuploidy, the incidence of non-mosaic segmental aneuploidy does not appear to be related to the age of the egg or sperm source. There is emerging evidence that embryos with this type of PGT-A result can result in successful pregnancies if transferred. However, the live birth rates reported thus far are much lower than those of embryos with a euploid PGT-A result. This is a new area of study, and the data on the reproductive potential and risks related to these types of embryos is currently very limited. We encourage all patients to consider keeping embryos with this type of PGT-A result stored. As more data becomes available, our guidance to patients will also continue to evolve.

As of March 2025, our clinic will transfer embryo(s) with non-mosaic segmental aneuploid PGT-A results. However, this option is only available if a patient has no other eligible embryos available for transfer. We require a genetic counseling appointment to review your embryo’s results as well as our current understanding of the risks and benefits of transfer. Before proceeding with the transfer of an embryo with a non-mosaic segmental aneuploid PGT-A result, the patient and their partner (if applicable) will also be required to sign a waiver acknowledging their understanding of this counseling.

There are several potential benefits of PGT-A. For patients with several good quality embryos, PGT-A is an additional tool that may assist in the ranking and selection of the best embryo for transfer. For patients whose embryos have PGT-A, we recommend the transfer of a single chromosomally normal (euploid) embryo which reduces the chance of multiples (e.g. twins or triplets) and the increased risk of complications associated with those types of pregnancies. PGT-A may also be helpful when a patient plans to freeze and store embryos for future attempts at pregnancy. Since embryos with aneuploidy are more likely to result in a failed transfer or miscarriage, PGT-A results provide additional information about the reproductive potential of those stored embryos and a more complete picture of what a patient has available for the future. Normal PGT-A results also reduce the likelihood of certain detectable chromosome conditions like Down syndrome, trisomy 13, or trisomy 18. Study outcomes have been mixed as to whether PGT-A helps increase implantation rates, reduce miscarriage risk, or increase the likelihood of a live birth. This depends, in part, on the characteristics of the individual patient (such as their age and medical history). If you are interested in learning more about PGT-A, we recommend you discuss this test with your physician and our genetic counselor. We can review your unique circumstances to help you determine if PGT-A is right for you.

Yes, and we believe these are important to acknowledge. First, PGT-A can add significant additional cost that may not be covered by insurance (see question 33). Some patients may have to undergo more than one IVF cycle to get an embryo that is eligible for transfer, further increasing their costs. Second, the embryo(s) must be frozen while PGT is performed so patients are unable to do a fresh transfer. Instead a frozen embryo transfer will be scheduled after the PGT results are available meaning the time to pregnancy may be delayed. Third, the PGT process involves a biopsy which poses a small risk of harm to the embryo(s) (see question 7). Fourth, there is a small (2%-3%) chance the lab may get inconclusive results for an embryo meaning they are unable to determine whether the embryo is chromosomally normal or abnormal. Fifth, patients may experience stress and anxiety related to their PGT-A results. For example, they may face a difficult decision regarding whether to transfer an embryo with mosaic PGT-A results. Finally, although uncommon, inaccurate PGT results may lead to the transfer of an embryo with a chromosome abnormality that was not detected (false negative) or the decision not to use an embryo with potential to result in a healthy pregnancy (false positive).

PGT-M is an option for many patients whose embryos or children are at risk to inherit a specific genetic condition and who wish to reduce that risk prior to pregnancy. Likewise, PGT-SR is an option for many patients with a chromosome rearrangement who wish to reduce the chance of miscarriage associated with their translocation or inversion. If you are interested in PGT-M or PGT-SR, the first step is for our genetic counselor and the PGT lab to review your abnormal genetic test results (see question 23). The lab will determine if they can develop a test that would reliably identify which of your embryo(s) are affected and/or chromosomally abnormal. Unfortunately, PGT-M or PGT-SR may not be an option in all cases.

Except for a few chromosome conditions (e.g. Down syndrome, Turner syndrome, Klinefelter syndrome, trisomy 13, and trisomy 18), PGT-A does not test embryos for any specific genetic diseases or syndromes.

To perform PGT-M or PGT-SR, you must be able to provide documentation of the specific genetic abnormality. For PGT-M, a copy of the abnormal genetic test results must be submitted to the lab. These results must contain the specific gene and the specific variant(s) for which the patient wants to test their embryo(s). For PGT-SR, a copy of the abnormal chromosome study (karyotype) documenting the specific translocation or inversion must be submitted.

An embryo with normal PGT-M results is predicted to be unaffected with the genetic condition for which it was tested. For autosomal recessive and X-linked conditions, PGT-M will also identify whether the unaffected embryo is a carrier for that condition or not. Abnormal PGT-M results mean the embryo is expected to be affected with or at risk for the genetic 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 amount of each chromosome with no detectable missing or extra pieces. The lab will look closely at the chromosome(s) involved in the parent’s translocation or inversion. PGT-SR typically cannot distinguish between embryos with normal chromosomes and those with a balanced translocation or inversion like the parent. Therefore, a child born after normal PGT-SR results should be offered chromosome testing prior to starting their own family to understand their own reproductive risks and options.

Once the lab receives the embryo biopsy samples and has received payment for the testing, results are expected within 2 weeks for PGT-A and 2-3 weeks for PGT-M or PGT-SR.

Our genetic counselor will call you by phone with your PGT results as soon as they are available. At that time, we will review how many embryos are eligible for transfer. After this discussion, a copy of your PGT report can also be shared with you through MyChart.

No, but this is a very common misconception. Embryos with normal 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 euploid (normal) PGT-A results compared to untested embryos 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.

Non-invasive prenatal testing (NIPT) is a blood test for a pregnant person that detects DNA from the placenta. There are several labs that offer NIPT, and they vary in which chromosome conditions are screened. NIPT typically screens the fetus for Down syndrome (trisomy 21), trisomy 18, trisomy 13, and the sex chromosomes (X and Y). Some NIPT may also screen for other chromosome abnormalities including triploidy (having an extra copy of every chromosome) and certain microdeletions (missing pieces of a chromosome that cause known syndromes such as 22q11.2 deletion syndrome, 1p36 deletion syndrome, and Cri-du-chat syndrome). The benefits of NIPT are that it can be done as early as 8-10 weeks of pregnancy, and since it is done on a blood sample from the pregnant person, there is no physical risk to the pregnancy.

There are two main reasons why someone might choose to do NIPT after already doing PGT-A. The first and most important reason is that PGT-A results are not 100% accurate. There is a small chance an embryo with euploid (normal) PGT-A results has a chromosome abnormality (such as Down syndrome), but PGT did not detect or report it (i.e. a false negative). The second reason to consider NIPT is that some versions screen for microdeletion syndromes as described above. These are chromosome abnormalities that are typically too small to be detected by PGT-A. If you choose to do NIPT after transferring an embryo with euploid (normal) PGT-A results, the most likely outcome is that the NIPT results will be “low risk” (normal).

There are also two main reasons why someone might choose not to do NIPT after doing PGT-A. The first is a possible additional out-of-pocket cost. The second reason is more complicated. Since NIPT is also a screening test, it is possible for the results to come back “high risk” for a chromosome condition when the baby does not have that condition. The likelihood of a false positive NIPT result depends on what condition is “high risk.” As you can imagine, this situation might cause someone to have significant stress/anxiety and may also lead them to do invasive prenatal testing like an amniocentesis, which has a small risk of causing pregnancy complications or miscarriage.

Patients should speak to their OBGYN about NIPT and which conditions would be screened. Genetic testing in pregnancy is always optional. While it is very reasonable for someone to elect to do NIPT after normal PGT-A results, this is a personal decision, and every test has pros and cons.

The results of PGT (all types) are highly accurate. However, it is still a screening test meaning false positives and false negatives can occur. If you transfer an embryo with normal PGT results, you should still consider whether you wish to confirm the normal PGT results through diagnostic prenatal testing such as chorionic villus sampling (CVS) or amniocentesis. Samples obtained through CVS or amniocentesis can be used to test the fetus for chromosome abnormalities and/or single-gene conditions. Results from a CVS or amniocentesis are considered diagnostic meaning they are the most accurate tests available during pregnancy. However, both procedures are invasive and therefore involve a risk of complications (e.g. infection) and a <1% chance of resulting in miscarriage. Your OBGYN or a genetic counselor can review these options with you as there are risks and limitations for each test that should be considered carefully.

No. PGT only screens for certain chromosome abnormalities (PGT-A or PGT-SR) or a specific single-gene condition (PGT-M). While normal PGT results are reassuring, there is always a small risk for a false negative result. PGT does not have the ability to guarantee the outcome of an embryo transfer, nor can it ensure the health of a child who is born. Every pregnancy has a risk of approximately 3%-5% to result in a child with a genetic condition or birth defect. No genetic test can eliminate this risk or identify all diseases or birth defects. There is always a risk for a child to have a medical issue, regardless of the screening performed.

All embryos will continue to be stored unless otherwise specified by the patient and their partner (if applicable). This includes embryos with abnormal PGT results even if they are ineligible for transfer at our clinic. A patient and their partner (if applicable) must complete an embryo disposition form if they wish to discard embryo(s) or donate embryo(s) for research.

PGT is always optional. If PGT is not right for you, there are several genetic testing options that can be performed during pregnancy. First, non-invasive prenatal testing (NIPT) is a blood test for a pregnant person that detects DNA from the placenta. It is also sometimes referred to as cell-free fetal DNA testing. There are several labs that offer NIPT, and they vary in which chromosome conditions are screened. NIPT typically screens the fetus for Down syndrome (trisomy 21), trisomy 18, trisomy 13, and the sex chromosomes (X and Y). Some NIPT may also screen for other chromosome abnormalities, including triploidy (having an extra copy of every chromosome) and certain microdeletions (missing pieces of a chromosome that cause known syndromes such as 22q11.2 deletion syndrome, 1p36 deletion syndrome, and Cri-du-chat syndrome). The benefits of NIPT are that it can be done as early as 8-10 weeks of pregnancy, and since it is done on a blood sample from the pregnant person, there is no physical risk to the pregnancy. However, NIPT is still a screening test, meaning false positives and false negatives can occur. NIPT does not typically screen for single-gene conditions and may not be right for those with a chromosome translocation or inversion, but this is an evolving area.

Chorionic villus sampling (CVS) and amniocentesis are two additional options for prenatal genetic testing. CVS can be performed in the first trimester between 10 to 13 weeks gestation, while amniocentesis can be performed in the second trimester between 15 to 24 weeks gestation. CVS and amniocentesis can be used to test for chromosome abnormalities and/or a specific single-gene condition. Both provide highly accurate genetic results. While CVS and amniocentesis offer advantages over NIPT, both tests are invasive so they can result in complications and pose a small (<1%) risk for miscarriage. If you are interested in prenatal genetic testing, we recommend you review the benefits and limitations of these options with your OBGYN or a prenatal genetic counselor.

The cost of PGT depends on many factors, including the type of PGT being performed, the number of embryos being tested, and which lab is performing the test. Our genetic counselor will provide you with an overview of pricing if your IVF plan includes any type of PGT. Our office and the performing lab can assist you in determining your insurance coverage and expected out-of-pocket costs for PGT. At this time, insurance coverage for PGT-A is very rare so patients usually pay all costs out of pocket.