This procedure is used where there is a concern that embryos may not be chromosomally normal, for example, where there is a known genetic problem, a history of unsuccessful treatments or several miscarriages or if the woman is in her late 30s or 40’s and she may be producing a greater number of abnormal eggs. A cluster of cells are removed from each viable embryo created once they reach the blastocyst stage and then tested for the 23 chromosomes to detect abnormalities. Only chromosomally normal embryos are then replaced. This treatment is available in all countries though some countries require a permit to undertake the treatment first.