Genetic Screening: a possibility to help with IVF

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Genetic Screening: a possibility to help with IVF

Genetic Screening, PGS, PGD - inFertile Life

In the area of assisted reproduction, we are used to jargon and difficult terms. And most recently, we have been hearing about PGS and PGD. What is it and how helpful can it be?

 PGD stands for Preimplantation Genetic Diagnosis

It involves screening single cells from embryos for genetic diseases and chromosomal disorders. It’s like a biopsy of your embryos.

PGD is performed during an IVF cycle, before the embryo is transferred into the womb.

It allows selecting embryos for transfer based on their genetic and chromosomal status. The goal is to identify abnormal embryos, so they will not be transferred, leaving unaffected embryos to be selected for transfer that are more likely to implant and develop into healthy babies. Apart from detecting diseases, PGD technology can also be used to determine the sex of the embryo prior to the transfer into the uterus.

PGS stands for Preimplantation Genetic Screening

It consists of the same technology used in PGD but for people with recurrent pregnancy loss or infertility. Embryos are biopsied for aneuploidy (missing or additional numbers of chromosomes), which is a leading cause of miscarriage and implantation failure.

The goal of PGS is to identify chromosomally abnormal embryos, so they will not be transferred leaving the chromosomally normal embryos to be transferred in the attempt to achieve a successful pregnancy.

What does the procedure involve?

After the eggs and sperm are collected and fertilisation has occurred, the embryos develop in the lab for a few days. When the embryo is at blastocyst stage of development, on day 5 or 6, a few cells are removed. The biopsied cells are then transferred to a small tube for PGD analysis. Once the biopsy is performed, the embryos are frozen and stored until the results are back.

Who should have PGD and PGS?

PGD is extremely useful for couples in which one or both of the partners are carriers of an inherited genetic disorder. It significantly reduces this risk of passing on a disease to the child.

We also anticipate that 30% of all embryos in women less than 35 years will be chromosomally abnormal. This is often the reason behind multiple miscarriages. So PGS helps identify normal embryos, avoiding the need to undergo multiple embryo transfer cycles.

PGD and PGS are usually recommended for:

  • Couples with a carrier of a chromosomal aberration
  • Couples with the occurrence of a hereditary disease related to the chromosome X.
  • Couples with a carrier of the so-called small chromosomal mosaics.
  • Couples with repeated reproduction losses.
  • Couples with repeated failure of the IVF Cycle.
  • Couples, where the testicular or epididymal sperm (obtained with the method MESA or TESE) were utilized for the egg fecundation.
  • Couples after an undergone chemo-/radiotherapy.
  • Couples with a genetic disease in the family (some monogenous diseases).
  • Couples of a higher age (especially if the woman’s age is over 35 years).

What are the risks of PGD?

  • There is a 0.1% risk that the embryo may be damaged during the biopsy procedure.
  • The is also the risk of an erroneous diagnosis which is about 1.3 %. Although unlikely, it is possible that one cell in the embryo may have different chromosome numbers than the other cells in the biopsy. This is referred to as mosaicism and will result in a misdiagnosis due to the fact that the information from the biopsied cell is not reflective of the entire embryo.
  • The opposite situation can also happen. The embryo could be denoted as a normal one, however, its chromosomal equipment would be pathologic. The risk of this error is about 4.3 %.
  • PGD and PGS may also show that all embryos are abnormal, leaving no embryos left for transfer, in which case the cycle is cancelled.

Andreia Trigo

Fertility NLP Coach and Nurse Specialist

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