FAQ'S

Frequently Asked Questions

PGT-A (PGS)

PGT-M (PGD)

What Is PGS

PGT-A (PGS) stands for pre-implantation genetic screening. It’s an innovative technique that is used to screen the number of chromosomes in embryos. This technology aids in the selection of genetically healthy embryos for transfer.

Why Is PGS necessary?

About 50% of human embryos derived via IVF (in vitro fertilization) are known to carry chromosomally abnormalities.

Even up to 40% of morphologically normal embryos harbor aneuploidies *. PGT-A (PGS) can improve pregnancy rates (70% pregnancy rate with PGT-A (PGS) vs 40% without PGT-A (PGS)) PGT-A (PGS) reduces incidence of early miscarriages and thus the number of IVF cycles the patient must undergo.

How is PGS performed?

If you choose to have PGT-A (PGS), you’ll firstly go through an IVF cycle to create embryos. The embryos are grown in the IVF lab until day 5. On the day 5 a few cells from the embryo are biopsied and tested for their chromosome content.

What are the indications for someone to choose PGS?

PGT-A (PGS) treatment is recommended to patients who have experienced frequent miscarriages or repeated IVF failures. It is also suggested when either of the partners are of advanced age and in cases where a high incidence of sperm aneupolidy is diagnosed.

What is embryo biopsy?

Embryo biopsy is a procedure where an embryologist removes a small number of cells from the outer layer of a 3 or 5-day-old embryo.

Can PGS be performed on day 3 embryos?

PGT-A (PGS) testing can be performed on embryos biopsied at either day 3 or day 5. According to ESHRE guidelines, only a single cell is removed for a biopsy on day 3 as the embryo at this stage contains only 8 cells. However, a day 5 embryo has a few hundred cells, thus it is possible to extract up to 6 cells during embryo biopsy.

Can PGS damage my embryos?

Though PGT-A (PGS) is an invasive procedure, it has no adverse effect on the embryo. Embryo biopsy and micro-manipulation of embryos is being carried out in laboratories across the world and has been used for investigating the presence of genetic diseases for over 25 years. Studies so far have shown these procedures are perfectly safe, and do not cause any increased risk to children born as a result.

Does PGS include all genetic diseases?

No genetic test can detect all potential genetic abnormalities. PGT-A (PGS) testing is mainly performed to rule the possibility of embryos carrying aneuploid chromosomes, thus can only detect numerical changes in chromosome number. Specifically, PGT-A (PGS) can identify any missing or extra chromosomes, PGT-A (PGS) screening cannot rule out single gene disorders, balanced structural abnormalities, uniparental disomy, and genetic imbalances including deletions and duplications. PGT-A (PGS) can detect some types of polyploidy but cannot detect polyploidy in which the sex chromosomes are found as a multiple of normal (triploidy 69, XXX and tetraploidy 92, XXXX or 92, XXYY).

What is the effectiveness of PGS for different indications?

The likelihood of a healthy pregnancy is increased to about 60% in women younger than 40 years when an embryo is identified as normal after PGT-A (PGS). As female aging has a strong association with an increased incidence of chromosomally abnormal oocytes, women over 40 years are reported to have a higher incidence of chromosomally abnormal embryos. When normal embryos are found, the likelihood of pregnancy is about 50%.

Is prenatal testing recommended in cases where PGS is performed?

Although PGT-A (PGS) is highly accurate, prenatal testing is advised due to the mosaicism in embryos. Mosaicism is a phenomenon in embryos where a segment of cells can carry aneuploid chromosomes while the remaining cells are normal. Prenatal testing is recommended to reconfirm the results of PGT-A (PGS). Moreover, prenatal testing may detect other abnormalities not tested for by PGT-A (PGS) like microdeletions and duplications. Pregnant mothers conceived via IVF should discuss their options for prenatal testing with their Obstetrician. Noninvasive prenatal testing could be also an alternative.

Can PGS help patients who have experienced several miscarriages?

There are many possible causes for miscarriage. About 50% of first trimester miscarriages are due to a chromosome abnormality. This may be related to a woman's age or a rearrangement in a parent's chromosomes that predisposes the couple to conceive pregnancies with chromosome abnormalities. PGT-A (PGS) can be performed for either of these possibilities. For women over 35, the greatest risk may be for aneuploidy, a pregnancy with the wrong number of chromosomes, such as Down syndrome. PGT-A (PGS) for aneuploidy screening offers these women a greater chance of a successful and healthy pregnancy.

What is PGD?

PGT-M (PGD) is an abbreviated form of Preimplantation Genetic Testing. PGT-M (PGD) is a diagnostic test performed on embryos to detect the presence of single gene disorders such as sickle cell anemia, thalessemia, cystic fibrosis etc. This test aids in the selection of disease free embryos and helps the couple conceive a genetically healthy baby.

Why should I undergo IVF for PGD if I have not been diagnosed with infertility?

Since PGT-M (PGD) is performed on embryo biopsy samples and multiple embryos are required for this purpose, it is necessary to undergo stimulating medications to ensure more than one mature egg can be retrieved, fertilized, and grown in the lab.

What should I know about infertility drugs?

Infertility drugs are used to stimulate the release of multiple egg follicles which will facilitate the production of multiple embryos. IVF medications have been used for over 20 years. Studies investigating long-term effects of exposure to these medications have demonstrated that these medications do not put the patient at risk for ovarian or other cancers.

How likely am I to get pregnant if I use PGD?

Human reproduction is very inefficient, and the likelihood of getting pregnant naturally in any given month is only around 10%. With the transfer of three embryos on average, the pregnancy rate of PGT-M (PGD) is 30-35%. Many other factors may make the likelihood of getting pregnant such as quality of the embryos and age of the patients. The decision regarding how many embryos to transfer is made together with the patient to maximize the likelihood of achieving pregnancy, but also to minimize pregnancies with multiple fetuses.

To perform PGD for a single gene disorder, is it required to have identified the mutation causing the disease?

Yes. It is necessary to identify the mutation causing the single gene disorder to proceed for a PGT-M (PGD) case.

Should PGS for aneuploidy screening be performed in conjunction with PGD testing?

Aneuploidy is a numerical chromosome abnormality. It is recommended that PGT-A (PGS) for aneuploidy screening be performed in conjunction with PGT-M (PGD) testing. Both tests can be done on the same embryo biopsy, and therefore no additional risk to the embryo is implicated. PGT-A (PGS) for aneuploidy screens for abnormalities in chromosome numbers that could cause miscarriage or could result in the birth of a baby with birth defects and mental retardation. Down syndrome is an example of a genetic disease that is caused by a numeric chromosome abnormality.

After the probe has been developed, how soon must IVF be completed?

After the probe has been developed, the IVF cycle and testing of embryos can be completed at the convenience of the patient and the clinic. The probe can be kept long term. Patients needing to delay IVF for longer than 6 months after the probe has been developed should make special arrangements with Anderson.

If PGD testing has been done for a previous cycle, is there still a set-up time required for another PGD cycle?

No, there is no pre PGT-M (PGD) work-up time necessary for subsequent PGT-M (PGD) cycles. This is because the same probe that was made for the couple can be used again for any future testing.

What are the types of genetic testing that PGD includes?

Chromosome abnormality or aneupolidy testing by analyzing the number of chromosomes,

Single gene disorders passed from parents by analyzing affected embryos

Feel free to contact us!

Preimplantation Genetic Testing (PGT-A (PGS))

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specialist to choose a
genetically healthy embryo.

Consultation

No. 150, Poonamallee High Road,
(Opp to Dasaprakash Hotel)
Chennai – 600 084.