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Preimplantation genetic testing

Overview

Preimplantation genetic testing (PGT) is a sophisticated technique used in conjunction with in vitro fertilisation (IVF) to screen embryos for genetic abnormalities before they are implanted in the uterus.

This process involves extracting a few cells from the embryo and analysing their DNA to identify specific genetic disorders or chromosomal aneuploidies.

There are three main types of PGT:

  • Preimplantation Genetic Diagnosis (PGD), which targets single gene defects;

  • Preimplantation Genetic Screening (PGS), which checks for overall chromosomal normality;

  • and Preimplantation Genetic Testing for Aneuploidy (PGT-A), which specifically looks for chromosomal imbalances.

The primary aim of PGT is to increase the likelihood of a successful pregnancy and the birth of a healthy baby, particularly for couples at risk of passing on genetic disorders or experiencing recurrent miscarriages.

Preimplantation Genetic Diagnosis (PGD)

Preimplantation Genetic Diagnosis (PGD) is primarily employed to detect single gene defects in embryos produced through IVF.

This detailed genetic analysis is especially crucial for couples known to be carriers of specific genetic disorders, such as cystic fibrosis, Huntington’s disease, or sickle cell anaemia.

By identifying embryos that are free from these single gene defects, PGD enables the selection of embryos with the best chance of developing into healthy offspring. The process involves the biopsy of a few cells from the embryo at the blastocyst stage, followed by rigorous DNA testing to pinpoint any genetic mutations.

As a result, PGD not only enhances the success rate of IVF procedures but also provides prospective parents with peace of mind, reducing the risk of inherited genetic conditions in their future children.

 

Preimplantation Genetic Screening (PGS)

Preimplantation Genetic Screening (PGS) focuses on assessing the overall chromosomal normality of embryos conceived through IVF.

This type of genetic testing is particularly beneficial for couples with a history of unexplained infertility, recurrent pregnancy loss, or advanced maternal age, as these factors often correlate with a higher risk of chromosomal abnormalities.

During PGS, a biopsy is performed on the embryos, typically at the blastocyst stage, to collect a few cells for chromosomal analysis.

Techniques such as comprehensive chromosome screening (CCS) or next-generation sequencing (NGS) are employed to detect aneuploidies – the presence of an abnormal number of chromosomes – which can lead to conditions like Down syndrome, Turner syndrome, or Edwards syndrome.

By selecting embryos with the correct chromosomal count, PGS aims to enhance the likelihood of a successful implantation, healthy pregnancy, and the birth of a chromosomally normal baby.

 

Preimplantation Genetic Testing for Aneuploidy (PGT-A)

Preimplantation Genetic Testing for Aneuploidy (PGT-A) specifically targets the detection of aneuploidies in embryos produced through IVF.

Aneuploidies refer to numerical chromosomal abnormalities, which can result in miscarriages, implantation failures, or congenital disabilities if undetected. PGT-A aims to screen embryos before implantation to ensure they have the correct number of chromosomes.

This genetic test involves the biopsy of embryos at the blastocyst stage, followed by comprehensive chromosome analysis using advanced techniques like next-generation sequencing (NGS) or array comparative genomic hybridisation (aCGH).

Couples who have experienced recurrent miscarriages, repeated IVF failures, or have advanced maternal age may significantly benefit from PGT-A. By identifying and selecting only embryos with the normal chromosomal number, PGT-A enhances the chances of a healthy pregnancy, reduces the risk of miscarriage, and increases the likelihood of giving birth to a healthy baby.

Furthermore, PGT-A provides valuable insights into the underlying causes of infertility and pregnancy loss, helping to tailor more effective fertility treatments.

 

Who Should Undergo Preimplantation Genetic Testing?

Preimplantation Genetic Testing (PGT) is particularly beneficial for certain individuals and couples facing specific reproductive challenges or risks. Those who should consider undergoing PGT include:

1. Couples with a history of genetic disorders: If one or both partners are carriers of genetic disorders, PGT can help identify embryos that are free of these conditions, ensuring the birth of a healthy baby.

2. Women of advanced maternal age: As the risk of chromosomal abnormalities increases with maternal age, women over the age of 35 may benefit from PGT to select embryos with the correct chromosomal number, thereby enhancing the chances of a successful pregnancy.

3. Couples with recurrent miscarriages: For those who have experienced multiple miscarriages, PGT can help diagnose chromosomal abnormalities that may be causing pregnancy loss and assist in selecting healthier embryos for implantation.

4. Couples with repeated IVF failures: If previous IVF attempts have failed, PGT might identify underlying chromosomal issues, improving the prospects of a successful implantation and pregnancy in subsequent attempts.

5. Individuals with a family history of genetic conditions: Those with known inherited genetic conditions may use PGT to prevent the transmission of these disorders to their offspring.

6. couples opting for family balancing: Some couples may choose PGT for non-medical reasons, such as selecting the sex of the baby for family balancing, provided it is legal and ethical in their country.

By undergoing PGT, these individuals and couples can significantly improve their chances of a healthy pregnancy and the birth of a chromosomally normal baby, while also gaining valuable insights into their reproductive health.

 

Process of Preimplantation Genetic Testing

The process of Preimplantation Genetic Testing (PGT) is meticulously structured to ensure it provides accurate results while maintaining the integrity of the embryos. The procedure involves several key steps:

1. Ovarian Stimulation and Egg Retrieval: The process begins with ovarian stimulation, where the woman undergoes hormone therapy to produce multiple eggs. These eggs are then retrieved from the ovaries using a minor surgical procedure.

2. In Vitro Fertilisation (IVF): Once the eggs are collected, they are fertilised with sperm in a laboratory setting to create embryos. This can be achieved through conventional IVF or Intracytoplasmic Sperm Injection (ICSI), depending on the specific circumstances of the couple.

3. Embryo Culture: The fertilised embryos are cultured in a lab for 5-6 days until they reach the blastocyst stage, which comprises around 100 cells and is suitable for biopsy.

4. Embryo Biopsy: A few trophoectoderm cells (the cells that will form the placenta) are carefully removed from each blastocyst. This biopsy is performed under a microscope and requires high precision to avoid harming the embryo.

5. Genetic Analysis: The biopsied cells are then subjected to genetic testing using advanced techniques. These tests can identify chromosomal abnormalities, genetic mutations, and specific genetic disorders. Various methods such as Next-Generation Sequencing (NGS), Fluorescent In Situ Hybridisation (FISH), or Polymerase Chain Reaction (PCR) may be employed depending on the specific type of PGT being performed.

6. Embryo Selection: Based on the genetic analysis, embryos that are free from the tested conditions and carry the correct chromosomal number are selected for transfer. These healthy embryos offer the best chance of resulting in a successful and healthy pregnancy.

7. Embryo Transfer: The selected embryo(s) are then transferred into the woman’s uterus during a subsequent cycle. This process is carefully timed to align with the optimal window of implantation.

8. Follow-Up and Pregnancy Testing: After embryo transfer, the woman is monitored closely, and a pregnancy test is conducted usually around two weeks later to confirm implantation and the establishment of pregnancy.

Each of these steps plays a crucial role in ensuring the success of PGT, offering couples a higher probability of achieving a healthy pregnancy and reducing the risk of genetic disorders in their offspring.

 

Benefits of Preimplantation Genetic Testing

Preimplantation Genetic Testing (PGT) offers numerous benefits for prospective parents, providing a higher level of confidence in achieving a healthy pregnancy.

One of the primary advantages is the early detection of genetic abnormalities, which can significantly reduce the risk of genetic disorders being passed on to the offspring. This early intervention allows couples to make informed reproductive choices based on their genetic profiles.

Another benefit of PGT is its ability to increase the success rates of in vitro fertilisation (IVF) by selecting embryos with the correct chromosomal number. This selection process not only enhances the likelihood of successful implantation but also reduces the chance of miscarriage, often caused by chromosomal abnormalities. As a result, couples may experience less emotional and financial strain through more targeted and successful IVF cycles.

PGT can also be instrumental for families with a history of specific genetic disorders. By screening embryos for these conditions, PGT provides an opportunity to break the cycle of inherited diseases, offering hope for healthier future generations.

Moreover, this testing can mitigate the need for difficult decisions regarding pregnancy termination following the diagnosis of genetic conditions through traditional prenatal testing methods.

In summary, Preimplantation Genetic Testing stands as a powerful adjunct to assisted reproductive treatments, delivering peace of mind to couples and enhancing the prospects of having healthy children.

 

Contact us

If you have questions or would like to explore the benefits of PGT further, please do not hesitate to reach out to us. We are here to help you understand the process and determine the best course of action tailored to your unique situation.

Contact us today to schedule a consultation and take the first step towards a healthier future for your family.

About Doctor

dr-amit-chakraborty-cancer-surgeon-in-mumbai

Dr. Supriya Puranik

Gynaecologist & IVF Specialist

Often known as the last glimmer of hope for people who have lost all hope for conceiving a child, Dr. Supriya Puranik is a leading gynaecologist, high-risk obstetrician and Head of IVF & Gynaecology department at Sahyadri Hospitals Momstory in Shivajinagar, Pune.

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  • Om Kadel

She is excellent. And as a goddess for my family. After long time I m blessed with twins baby due to her efforts only. She used to boost me with lots of positive thoughts whenever I lost the hope. You are too supportive mam. Thanks a lot.

Even the hospital staff, Nurses, mousis,house keeping staffs are at your step when ever needed when I was admitted.

The food provided is well planned according to the diet of patients by mam. Thank you very much mam for this turn over in my life after 12 years of marriage.

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Dr. Supriya Puranik’s mam is very sweet person I have ever met. She is very caring, her ever smiling face always gives you positive wives. Staff is also very helpful and care taking during delivery, the best hospitality service I would say…
Thank you so much Dr Puranik Mam and Team. keep up the good work

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