Prenatal diagnosis employs a variety of techniques to determine the health and condition of an unborn fetus in high risk pregnancies. It is evident that more than 50% of first trimester spontaneous abortions are due to chromosomal abnormalities. The most common cause of spontaneous abortion is numerical chromosome imbalances (aneuploidies), particularly of chromosomes 13, 14, 15, 16, 18, 21, 22 and X. Aneuploidies of five particular chromosomes (13, 18, 21, X, Y) account for 80-95% clinically relevant cytogenetics abnormalities that lead to infants born with congenital defects.

Risk of Chromosome Abnormalities Increase with Maternal age