 Rationale: Conventional prenatal diagnosis PND for single-gene disorders requires invasive procedures, either chorionic villus sampling between 11 and 14 weeks gestation or amniocentesis after 15 weeks. Although these approaches to obtain foetal DNA currently provide the golden standard for PND, the invasive procedures carry a risk of miscarriage of 0.5-1. A reliable non-invasive alternative has long been sought. Circulating cell-free foetal cff nucleic acids DNA and RNA, which are present in maternal blood during pregnancy, can be used for non-invasive prenatal testing NIPT. NIPT for some chromosomal anomalies trisomy 21, 13, 18 is now validated. NIPT for other chromosomal anomalies is still under development. NIPT of single-gene disorders is technically very challenging, due to the predominance of maternal DNA sequences, Some small studies have shown that a very limited number of monogenic genetic disorders can currently be diagnosed in maternal blood. In general de novo mutations in the foetus and paternally transmitted disorders are less difficult to diagnose than maternally transmitted disorders. 