Abstract
Routine amniocentesis is an established test for the prenatal diagnosis of chromosome abnormalities and many single-gene conditions. Chorionic villus sampling and early amniocentesis, which are available in some centers, enable families to receive prenatal test results earlier in the pregnancy. There are concerns regarding the safety of early pregnancy testing because of increased risks for pregnancy loss and possible risks for birth defects. The use of first trimester testing has changed because of these concerns, and alternative methods of screening pregnancies at risk for a chromosome abnormality are being investigated.