Array CGH
Approximately 70% of embryos produced either through natural conception or IVF are lost before birth. A major cause of embryo loss, including miscarriage, is a chromosome anomaly (known as aneuploidy) where there is either a loss or gain of a chromosome. Using the technique of Polar Body Array CGH, it is possible to screen all the chromosomes of a human egg prior to the creation of the embryo.
During the procedure, a microscopic structure called the polar body that lies between the egg itself and its outer 'shell', and contains a copy of all the chromosomes in the egg, is removed before the egg is fertilised. The polar body of each egg is tested using the Array CGH method, providing us with information on the complete chromosome make up of the egg. In this way we can screen for the chromosomally normal eggs. As the polar body is a 'surplus' structure within the egg and normally disappears a few days after fertilisation, this is an ideal way of testing the chromosome material without disrupting the actual chromosomes within the egg itself.
The technology of Array CGH has the potential to:
- Greatly improve IVF birth rate per embryo transferred
- Minimize the incidence of miscarriages and birth defects caused by irregularity in the chromosome number of eggs (and conditions such as Downs, Edwards or Patau Syndromes)
- Reduce the incidence of multiple pregnancies whilst maintaining a high live birth rate
Array CGH is suitable for all patients. It is particularly suitable for the following groups: women who are aged over 37; men who have been shown to have sperm at risk of carrying abnormal chromosomes; couples who have had several miscarriages or several attempts at IVF but failed without explanation. But, knowing that even the younger female is at risk of up to half her eggs carrying a chromosome anomaly, it could be argued that using Array CGH to effectively eliminate all such eggs or embryos will increase the chance of success for those couples.
