This method allows for the diagnosis of known genetic diseases – of which one or both members of the couple may be carriers or may be suffering – in embryos resulting from in vitro fertilisation, so that only healthy ones may be transferred to the uterus.
To that end, when the fertilised ova are at the 8-cell or at the blastocyst stage, an ‘opening’ is made in the shell of the ovum (zona pellucida) under a microscope and with the aid of a laser beam. Through this opening a cell is collected – if the biopsy is performed at the 7- to 8-cell stage – or five to ten cells are collected – at the blastocyst-stage – which are then sent to the genetics lab to be genetically analysed.
Thus, monogenetic disorders (e.g., cystic fibrosis, thalassemia), X- chromosome sex- linked disorders (e.g., Duchenne muscular dystrophy, haemophilia) or chromosomal anomalies (e.g. trisomy) can be diagnosed. Judging from the children that have been born to this day, it seems that pre-implantation diagnosis is accurate and safe.
