19 October 2010
Three healthy babies have been born in a pilot study of a technique to screen eggs across the full range of chromosomes, looking for defects that boost the risk of miscarriage, doctors said on Friday.
It is the first controlled trial of a technique called microarray comparative genomic hybridisation (CGH), which aims at boosting success in assisted reproduction. The first birth using CGH occurred in Britain last year: a baby called Oliver, who was born to a 41–year–old woman who had had 13 failed attempts at in–vitro fertilisation (IVF).
Human cells have 46 chromosomes, with 23 inherited from each parent. Before an egg is fertilized, it ejects half of its full set of chromosomes to make room for the 23 coming from the sperm. These discarded chromosomes, held in a structure called the "polar body," are a mirror image of those remaining in the egg.
CGH examines this cast–off genetic material. If there are too few or too many chromosomes, doctors know that the egg is not suitable for use. CGH screening has several advantages. Firstly, it tests all 23 pairs of chromosomes in a cell, rather than a limited number, as other methods do, ESHRE said.
In addition, the cell tested is taken from the egg at fertilisation, rather than from a developing embryo. The technique could be a boon in countries which outlaw embryo analysis.