Rapid aneuploidy testing versus traditional karyotyping: is it better to know more?

Chromosomal anomalies remain the commonest cause of mental retardation and congenital malformation. Traditionally, the prenatal diagnosis of chromosomal aberration relies on cytogenetic analysis of the cells obtained from amniocentesis or chorionic villus sampling (CVS). First, the amniotic fluid or chorionic villi samples need to be cultured for 14 days or more before adequate foetal cells can be harvested. Then the cells are spread on slides and stained. Finally, the copy number and the structural arrangement of each chromosome are examined. This procedure, called karyotyping, has for many years been the gold standard for prenatal diagnosis of chromosomal anomalies in developed countries and in Hong Kong.