• Pre-implantation Genetic Screening
  
  Pre-implantation genetic screening (PGS) is often considered an alternative to prenatal diagnosis. PGS is a process whereby 2 cells are extracted from an eight cell embryo and screened for any genetic / chromosomal abnormalities. It's main advantage is that it avoids selective pregnancy termination as the method ensures a pregnancy free of the disease under consideration.

Currently, there are mainly two groups of patients for which PGS is indicated.

• The first group consists of couples that undergo IVF treatment and whose embryos are screened for chromosome aneuploidies. The main indications for aneuploidies are an advanced maternal age, a history of recurrent miscarriages or repeated unsuccessful implantation. It has also been proposed for patients with obstructve and non-obstructive azoospermia.
  
• The second group consists of couples with a high risk of transmitting an inherited condition. This can be a monogenic disorder, meaning the condition is due to a single gene only, (autosomal recessive, autosomal dominant or X-linked disorders) or a chromosomal structural aberration (such as a balanced translocation). PGS helps these couples identify embryos carrying a genetic disease or a chromosome abnormality, thus avoiding the difficult choice of abortion.

Couples referred for PGS are known to be at genetic risk due to an affected family member or the birth of an affected child and may:

a) have a history of prenatal diagnosis and termination of an affected pregnancy (TOP)

b) have a moral or religious objection to TOP

c) have a previous history of recurrent miscarriages due to chromosomal abnormalities.

d) be infertile and carrying a generic abnormality (which may or may not be causing their infertility)

e) advanced maternal age

f) repeated implantation failures

 

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