Fluorescent In Situ Hybridization
Pre-Implantation Genetic Screening (PGS) allows for the screening of embryos during In Vitro Fertilization (IVF) in order to identify numerical chromosomal abnormalities (aneuploidy). Aneuploidies of 13, 18, 21, X and Y chromosomes account for 90-95% of all live born chromosomal abnormalities.
FISH Technology Advantages
Analyze aneuploidies of 5 chromosomes (13, 18, 21, X and Y) ;
The accuracy of FISH testing is about 95%;
Convenient and rapid;
Can be performed with day 3, 5 or 6 embryos;
Embryos are able to be transferred fresh or frozen;
Detect the following disorders:
Trisomy 21 (Down syndrome);
Trisomy 18 (Edward syndrome);
Trisomy 13 (Patau syndrome);
45,X (Turner Syndrome);
47,XXY (Klinefelter Syndrome);
47,XXX (Triple X syndrome);
47,XYY (Jacob’s syndrome).
The FISH-based FISH benefits
Reduces miscarriage rates;
Increases ongoing pregnancy rates;
Fewer cycles of IVF treatment needed (less time and money);
Greater chance of having a healthy baby.
Who should use FISH-based FISH test?
Women over the age of 35;
Family history of Trisomy (21, 18, 13);
Concern for a pregnancy with a Trisomy;
Concern for a sex-linked gender illness ;
Recurrent pregnancy loss;
Recurrent failure of IVF treatment.
The FISH-based FISH Process
IVF Couple undertakes In Vitro Fertilization (IVF) cycle to create embryo;
Embryo Biopsy (Day 3,5 or 6) The highly skilled embryologist carefully removes a small cell sample from each embryo;
FISH-base PGS Analysis The 5 chromosomes (13, 18, 21, X, and Y) in the embryo are analyzed to determine healthy, normal number of chromosomes;
Embryo Transfer A chromosomally normal embryo is selected for transfer back in the womb. Additional embryos with normal number of chromosomes can remain frozen for future use.
FISH cannot fully access all the chromosomes. 5 chromosomes PGS by FISH detects aneuploidy of chromosomes 13, 18, 21, X, and Y. This means that many abnormal embryos, incapable of forming a successful pregnancy, remain undetected and may be transferred., incapable of forming a successful pregnancy, remain undetected and may be transferred.
This FISH analysis is unable to detect abnormalities caused by the following factors: chromosome mosaicism, chromosome structural abnormalities (translocation, inversion, duplication and deletion), uniparental disomy (UPD), single/ multigenic disorders and other abnormalities. (FISH) chromosome mosaicism, chromosome structural abnormalities (translocation, inversion, duplication and deletion), uniparental disomy (UPD), single/ multigenic disorders;
PGS is limited by the technology and the number of cells examined. If the biopsied cells are normal it doesn’t necessarily mean that every cell in the embryo is also normal. The embryo could be mosaic, and depending on the severity, it may be unable to develop normally after transfer. Ongoing pregnancies are strongly recommended to undergo routine prenatal diagnosis.