• Fertility clinics
• Human embryo research
  • Approved research
  • Awaiting approval

Analysis of chromosomes in human preimplantation embryos using FISH and CGH (R0169) 

Certain IVF patient groups have been identified as being at high risk of producing embryos with chromosomal abnormalities. These chromosomal abnormalities usually cause failure of implantation following repeated IVF embryo transfers, or miscarriages. In a minority of cases the embryos can develop to cause a pregnancy affected by a chromosomal abnormality such as trisomy 21 (Down’s syndrome).

Preimplantation genetic screening (PGS) is a technique, which allows embryos produced during an IVF treatment cycle to be tested for specific chromosomal abnormalities.

Following the screening procedure only embryos that are identified as being normal for the chromosomes being analysed are considered for embryo transfer. Due to the increased selective power provided by this procedure, PGS may reduce miscarriage rates and improve both implantation rates and live birth rates in specific patient groups.

The screening process involves looking at the chromosomes present in a single cell taken from a 3 day old embryo. PGS relies on the fact that chromosomally, this cell should be an identical copy of the remaining cells in the embryo.

By inference if the cell is normal, it likely came from a normal embryo, and if it was abnormal from an abnormal embryo. Previous studies have shown that many human embryos are not made up of chromosomally identical cells. These embryos are called mosaic embryos. Mosaicism can affect the reliability and hence the benefits of PGS.

Our study aims to analyse single biopsied cells using comparative genome hybridization (CGH) or microarray techniques both of which can detect all the chromosomes in the cell.

The results will be compared with the results obtained from the remaining embryo using FISH (a simpler technique able to reliably detect between 5 and 9 chromosomes in a single cell). This strategy will allow us to further investigate the incidence of mosaic embryos and the degree of mosaicism. In this way, we may be able to determine whether mosaicism is linked with a specific patient profile, such as age or IVF techniques such as embryo freezing and what degree of mosaicism an embryo can tolerate. This will ultimately improve the management of patients requesting PGS and help our understanding of early human development.

 

Back to research we have approved

Page last updated: 11 April 2009

• Send to a friend