Over the same period, our understanding of preimplantation genetics and early human development has also been revolutionised. We now know that human eggs and embryos have an exceptionally high incidence of chromosome abnormalities and that these are a major cause of IVF failure, miscarriage and in rare cases affected live births. PGT for chromosome aneuploidy (abnormal number of chromosomes) is now used widely to select euploid embryos (with normal chromosome copy number) for transfer. I hope you find this site informative and useful and look forward to your feedback. - PROFESSOR ALAN HANDYSIDE