Preimplantation Genetic Screening

Written by: Dr. Mohammed Agdi

 

 

 

 

 

 

 

 

Numerous Preimplantation Genetic Screening (PGS) is now possible. This technology performs a comprehensive chromosomal screening through which we help couples to achieve their goal of having a healthy baby. While some IVF patients can benefit from PGS, it is offered to the following patient groups:

 

• Recurrent Miscarriage.

• Advanced Maternal Age

• Male Infertility

• Repeated IVF Failure

• Chromosomal Structural Abnormalities: Translocations, Inversions and Deletions.

• Aneuploidy

 

Chromosome translocations are abnormalities of a chromosome’s structure. Translocations occur when fragments or pieces of a chromosome break off and rearrange onto a different chromosome or rearrange within itself. Balanced translocations contain all genetic information, but pieces of chromosomes have switched places resulting in no gain or loss of chromosome material. Unbalanced translocations result in an individual having more or less chromosomal material, thus causing genetic defects.

 

Aneuploidy is a condition which involves a cell with an incorrect number of chromosomes—too many or too few. Chromosomes contain all genes and DNA; the building blocks of the body. Humans have 46 chromosomes, or 23 pairs. These include chromosomes 1 to 22 (the autosomes) and chromosomes X and Y (the sex chromosomes). During fertilization, an embryo receives 23 chromosomes from the sperm and 23 chromosomes from the egg to form either 46,XY (normal male) or 46,XX (normal female). Aneuploidy disorders do not typically run in families and can include Down syndrome, Trisomy 18, Trisomy 13 and Turner syndrome. Aneuploidy testing of preimplanted embryos can determine these chromosomal disorders in addition to the sex of the embryo before transferring them back to the uterus.

 

PGS is performed as a part of a standard IVF cycle where multiple eggs are produced, retrieved from the ovaries and fertilized with the husband's sperm in the Embryology Laboratory. IVF gives us access to embryo(s) in vitro. PGS is then performed by removing one or two cells from each embryo through a procedure called embryo biopsy. These cells are analyzed for the presence of chromosomal abnormalities that may contribute to failure of pregnancy. This sophisticated and technologically advanced testing attempts to identify embryos which are free of abnormalities and more able to achieve the patient's goal of having a healthy baby.

 

In some situations, embryos may need to be frozen in case the testing results will take longer time to be available and the embryos will be transferred into the uterus in a future cycle.

 

Informed Consent for the treatment is essential and has to be completed by both husband and wife.