Abbott Molecular Inc.: Prenatal Testing

Through prenatal testing, you can learn much about your child before it is even born, such as whether your child is a boy or a girl. You also may want to know the risk of genetic abnormalities that could impact the mental and physical development of your child. Prenatal testing is used to diagnose abnormalities in the fetus.

In every pregnancy, there is a slight chance that the fetus may have an extra, missing or rearranged chromosome. Many times, if there is an extra or missing chromosome, the pregnancy miscarries naturally. In fact, an estimated 90 percent of chromosomal abnormalities in the fetus result in miscarriage. About 85-90 percent of babies born with major abnormalities have either trisomy 21 (Down syndrome)**, trisomy 18, trisomy 13, or an abnormal number of sex chromosomes (X and Y).

Prenatal testing methods used to screen the health of the fetus include ultrasound and the "triple screen" or "multiple marker test." Ultrasound uses sound waves to create an image of the developing fetus. The triple screen or multiple marker tests measure the level of critical fetal proteins in the mother´s peripheral blood. If indicated by abnormal results from these screening tests or other reasons, fetal cells can be obtained for analysis by amniocentesis, chorionic villus sampling (CVS), or drawing blood from the fetal umbilical cord. Amniocentesis is the most commonly used method to collect fetal cells. The procedure is performed by an obstetrician usually in the 15th week of pregnancy or later. The obstetrician inserts a needle through the mother´s abdominal wall and removes fetal cells (amniocytes) from the fluid-filled sack surrounding the fetus. Standard cytogenetic testing (karyotyping) can be done to assess all cells for chromosome abnormalities. Test results are usually available in seven to 10 days or more. When an abnormality is suspected late in a pregnancy or when complications require an immediate diagnosis, the need for a prenatal test that provides rapid and accurate results is essential.

**About 5% of Down syndrome cases are not associated with classical trisomy 21. Instead, they result from other structural chromosomal abnornalities (such as Robertsonian translocations) that cannot be detected by the AneuVysion test.