Amniocentesis and chorionic villus sampling

Abstract This chapter reviews amniocentesis and chorionic villus sampling (CVS) to obtain tissue of the same genetic origin as the fetus for diagnostic purposes (most often testing for chromosomal abnormalities) without removing any tissue from the fetus itself. Second-trimester amniocentesis is a very effective test: failure to make a diagnosis is very rare. It involves a small risk of fetal loss, estimated at about 1 in 100 pregnancies. CVS is somewhat less effective, comparably safe if performed transabdominally, but less so if performed transvaginally.