Preimplantation Genetic Screening

Preimplantation Genetic Screening

Preimplantation Genetic Screening (PGS) tests embryos created through in-vitro fertilisation (IVF) before they are implanted in the uterus. In this procedure, one or more cells are extracted from the embryo to check for chromosomal abnormalities, known as aneuploidy.

By using this screening, healthcare providers can select embryos with the correct number of chromosomes for implantation, increasing the chances of a successful pregnancy.

Who Should Consider Preimplantation Genetic Screening?

Preimplantation Genetic Screening (PGS) isn't necessary for everyone. Women over 37 years old are more likely to have eggs with the wrong number of chromosomes, making screening important for those looking to conceive. Research shows that chromosomal abnormalities are a common reason for fertility issues and can increase the risk of miscarriage or having a baby with Down syndrome.

There are other situations where your doctor might suggest PGS, including:

  1. A family history of chromosomal problems
  2. Sperm with a risk of chromosomal abnormalities
  3. Previous miscarriages
  4. Unexplained failed IVF attempts

However, it's important to note that PGS does not guarantee a successful pregnancy or prevent miscarriage, and research on its effectiveness in these cases is still limited.

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Which Test Do You Need?

Depending on your situation, you may need Preimplantation Genetic Screening (PGS) for various reasons. Here are two main types of testing:

1. Testing for Monogenic Diseases

This involves analysing specific gene mutations inherited from both parents. These mutations can lead to diseases caused by changes in DNA. Examples include cystic fibrosis and sickle cell anaemia, as well as inherited mutations that may increase the risk of breast or ovarian cancer. Common diseases tested include:

  1. Huntington's disease
  2. Sickle cell anaemia
  3. Cystic fibrosis
  4. Muscular dystrophy
  5. Fragile-X syndrome
  6. BRCA1 and BRCA2 mutations
  7. Tay-Sachs disease

2. Testing for Chromosomal Structural Arrangement

This analyses embryos from parents who have chromosomal rearrangements, such as inversions or translocations, which can lead to miscarriages. Common disorders examined include:

  1. Reciprocal translocations
  2. Non-reciprocal translocations
  3. Robertsonian translocations

Based on your specific condition, PGS can help identify potential complications that may arise during pregnancy.

Preimplantation Genetic Screening

How Does IVF-PGS Work?

Preimplantation Genetic Screening (PGS) typically takes a biopsy when the embryo reaches the blastocyst stage, around the fifth or sixth day of development. The embryos are frozen at the clinic while the biopsies are analysed in the lab.

Each embryo biopsy is examined during screening to count the number of chromosomes. The results can show either an average number of chromosomes, indicating a higher chance of a healthy pregnancy, or an abnormal number, which may suggest risks like miscarriage or other complications.

After the analysis, a genetic report is provided to the healthcare professional. Based on this report and the grading and appearance of the embryos, the doctor will recommend which embryos are best suited for implantation for couples trying to conceive.

Indications and Conditions for PGS

Preimplantation Genetic Screening (PGS) is recommended for couples with single-gene disorders or structural chromosome abnormalities. While there are no strict conditions for undergoing PGS, it is often considered for women over 35 or those who have experienced failed IVF attempts or miscarriages.

What is Preimplantation Genetic Diagnosis (PGD)?

Preimplantation Genetic Diagnosis (PGD) offers insights into the genetic makeup of embryo cells. During this process, 3 to 8 cells are extracted from the embryo on day five and sent to a lab for testing. The embryo is then frozen for later implantation. PGD can detect nearly 2,000 inherited single-gene disorders and accurately identify affected and unaffected embryos with up to 98% precision.

What is the Cost of Preimplantation Genetic Testing?

Preimplantation Genetic Testing (PGT), commonly called Preimplantation Genetic Screening (PGS), is not a standalone procedure but part of the broader IVF process. As a result, the overall cost can be significant, typically averaging around ₹5,000 to ₹1,50,000. This fee includes consultations, lab expenses, medications, additional tests, and follow-up visits.

Pros and Cons of Preimplantation Genetic Testing

When considering PGT, evaluating the pros and cons is essential, especially given its expense.

Advantages of PGT:
  1. Reduced Risk of Chromosomal Issues: Lowers the likelihood of having a child with chromosomal abnormalities.
  2. Support for Women with Past Miscarriages: This can help women who have experienced unexplained miscarriages prevent future occurrences.
  3. Informed Choices: Assists in making decisions about continuing or terminating a pregnancy if abnormalities are detected.
  4. Benefits for Older Women: For women over 36, PGT can decrease miscarriage risks and reduce the number of embryos needed for implantation.
Disadvantages of PGT:
  1. High Cost:The procedure can be financially burdensome.

Alternatives to IVF-PGS

Some of the alternative methods which are likely to work better include –

  1. Chronic villus sampling
  2. Amniocentesis
  3. Ultrasound and Blood Tests
  4. In case of a high risk of inherited diseases, one might consider donor eggs or sperm.

Thus, PGS is an additional test that might be carried out. If couples want to undergo the procedure, they should consult the medical professionals beforehand.

Preimplantation Genetic Screening



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