Smaller family size and advancing parental age have increased the demand for prenatal diagnosis.
Prenatal cytogenetic diagnoses currently used, such as amniocentesis and chorionic villus
sampling, are usually not preferred by the expectant couples due to the risk imposed on the mother and child. High false positive rates (5%) of current non-invasive screening methods, such as serum analysts or ultrasound, cause a large number of unnecessary invasive practices to be performed, which apart from the associated risk, place considerable psychological distress on the couples
involved (Wald et al., 1999). (Copied from article).