About 250 pregnancies are affected by chromosomal abnormalities each year in NSW (See Chapter 9). Over 7,000 chromosomal tests for prenatal diagnosis of congenital abnormalities by amniocentesis or chorionic villus sampling (CVS) were carried out in NSW in 2000, having increased from 3,869 in 1990. Amniocentesis is the most common test used in NSW for prenatal diagnosis of chromosomal abnormalities, and is used twice as frequently as CVS.