For couples facing serious problems with fertility issues and childbirth, here is a test to improve the odds for parents going through In Vitro Fertilisation (IVF).

The Preimplantation Genetic Screening (PGS), the procedural carried out on IVF embryos to find its genetic status before transfer. It is considered as an important tool for evaluating the genetic status of embryos and can help to have a healthy baby.

WHO ARE RECOMMENDED

  • The Preimplantation Genetic Screening is specifically recommended for
  • Advanced Maternal age, i.e., 35 years and above
  • Recurrent miscarriages
  • IVF failures
  • On considering a low quantity and quality of sperm

Significance

  • It is performed on the embryo before it is transferred.
  • It allows the identification and transfer of embryos free from aneuploidies to the mother.
  • Increases pregnancy rates per transfer.
  • Reduces the time needed to achieve pregnancy.

Beneficiaries of PGS

  • This most preferential option is available for individuals or couples undergoing In Vitro Fertilisation (IVF).
  • To improve pregnancy rate
  • To reduce the miscarriage rate for women with frequent recurrent miscarriage
  • It is beneficial for women of age 35 and over.
  • Preferred for individuals or couples who had repeated failed in IVF cycles.

Understanding Preimplantation Genetic Screening

This involves understanding basic genetic testing of embryos. The only way to create embryos for PGS is through IVF or ICSI treatment. Healthy pregnancy begins with healthy embryo. Specific counselling would be given to couples undergoing treatment to create embryos.

One egg has 23 Chromosomes and so as one sperm. A fertilized egg has half of mother’s DNA and half of father’s DNA.

After fertilization, a healthy egg begins to grow with 46 chromosomes. On this formation, there are chances of missing chromosomes, either one or many. This leads to miscarriage or birth defect. The chances of such abnormality are around 40 – 50% for both younger and older couples.

The results of this test usually take up to 4 weeks from the time of biopsy to process.

In addition, there are challenges for those who undergo IVF process with possibility of multiple attempts. This leads to high cost financially, bringing emotional stress psychologically and physically. When there is a transfer multiple embryo to improve the chances of pregnancy, the probability of twins and triplets increases.

Benefits

  • PGS increases the rates of implantation and childbirth
  • Reduces time between IVF cycles
  • Lowers the risk of miscarriage and early pregnancy
  • Eliminates the chromosomal abnormality such as ‘Down Syndrome’, a genetic disorder that are caused by an additional copy of chromosome.
  • Reduces the risk and cause of multiple pregnancy
  • Women aged 35 and over, improved pregnancy rates are high.

HOW IT WORKS

The fertilized egg divides into two, four, eight and so on. On day 5, there are about 128 cells created. One cluster of cells becomes Fetus and the other Placenta.

During the process, the embryologist uses a small tool, 120th diameter thickness of a human hair to remove few cells from the cluster that will become Placenta. Then the sample undergoes genetic testing.

Lab process

  • DNA copies are made with the safe cells.
  • Count the chromosomes in each cell removed from each of developing embryos.
  • The data are passed to the clinic, where the couples can make decision with consulting the doctor for treatment to transfer a healthy embroyo.
  • Then starts chances of pregnancy with lower risk of complications.
  • Other embryos can safely be frozen for future use.

Results Based On PGS Analysis Of Embryos

Possible results that can be generated from PGS

Normal Embryo

Shows a normal number of chromosomes and suitable for transfer

Abnormal Embryo

Shows significant deletions of chromosomes and not suitable for transfer.

Partial Deletions 

Shows a small amount of genetic information missing from one or more chromosomes but not complete loss of a chromosome.  Some of these embryos may be suitable for transfer but may have less chance of pregnancy.

Mosaic

Shows a mixture of normal and abnormal cells within those analyzed. Some of these embryos may be suitable for transfer but may have less chance of pregnancy.

No Result

It is not possible to analyze the genetic information sent to the lab. This happens in approx. 5% of embryos biopsied.

Dr Arun Muthuvel, MBBS, MS – OBGYN, Mch – Reproductive Medicine and Surgery is the Medical Director of Iswarya Fertility Centre, Chennai

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