Overview of Prenatal Testing

Ultrasound

Most doctors today use routine ultrasounds to help them determine things such as the presence of multiple fetuses, the position of the placenta, the due date of the baby, and birth defects, as well as to keep track of fetal growth.

Targeted ultrasounds may help doctors evaluate specific organs that are at risk for genetic abnormalities, and fetal echocardiograms help doctors check the fetus’ heart structure when there is a question about the possibility of fetal heart disease or abnormality.

Using a painless transducer, which bounces high frequency sound waves through the mother’s abdomen and at the fetus, the doctors are able to receive a visual image created by the echoes.

Although many studies have shown that there is no evidence to suggest that the fetus can be harmed by ultrasound, the new trend of capturing 3-D ultrasound images for non-medical purposes has some doctors concerned that the overuse of the technology may not be completely safe during pregnancy.

Quad Marker Screening

A Quad Marker test screens for the possibility of Down syndrome, neural tube defects, and other chromosome duplications. It measures the amount of alpha-fetoprotein (AFP), unconjugated estriol (uEST), inhibin_A, and Human choronic gonadotropin (hCG) in your blood.

Studies have shown that women that are carrying babies with Down syndrome have levels of the various hormones outside the normal ranges.

This blood test is usually performed between the 15th and 20th weeks of a pregnancy. It is important to remember that the Quad Marker test is only a screening test and is not diagnostic. If the results, which take about two weeks to become available, are abnormal, your doctor may suggest further testing, such as an amniocentesis.

Nuchal Translucency (NT)

One of the newer tests available, the NT screening helps to determine the risk of Down syndrome by using high-resolution ultrasound to examine the nuchal area (the fold of skin at the back of the neck) of the fetus. Using a numerical formula that combines the ultrasound test results with a series of blood tests and the woman’s age, the NT can detect the potential for Down syndrome in about 80 percent of women.

Because it is only a screening test, however, women who have positive results or high numbers in an NT exam are usually offered to follow up with an amniocentesis or chorionic villi sampling (CVS) test for more definitive results.