Screening in Pregnancy - [Narrator] Prenatal screening tests provide you with information regarding the risk for certain conditions in your pregnancy. (mellow music) Screening is performed on a blood sample from the pregnant woman, and in some cases, ultrasound. Screening will not hurt the baby. Screening tests will tell us if there is a higher or lower risk of a specific abnormality. They will not say with certainty if a baby is affected. The majority of these tests were initially developed to screen pregnancies for Down syndrome. Down syndrome occurs when a person has an extra chromosome 21. People with Down syndrome are unique individuals with their own personality, opinions, interests, and needs. People with Down syndrome are expected to have some degree of intellectual impairment, a characteristic appearance, and some potential health problems such as heart defects. Most of the prenatal screening tests have evolved to include other more severe chromosome abnormalities, too, like trisomy 13 and trisomy 18. Trisomy 13 and trisomy 18 are more rare than Down syndrome. Although these are separate conditions, both trisomy 13 and trisomy 18 typically cause a baby to have many birth defects. This most often results in death shortly after birth, or significant, life-long medical concerns. There are different types of screening tests. We are going to review two types of screening tests, first trimester screen and cell-free DNA or CF DNA screening. First trimester screen, or FTS. The FTS has two parts. Blood work from mom and an ultrasound of baby in the first trimester. The blood work from mom is used to look at hormone levels in your blood during pregnancy. The ultrasound is done around 12 weeks gestation and is used to take a measurement of the back of the baby's neck called the nuchal lucency. Using this information, the FTS provides patients with a risk estimate for Down syndrome, as well as trisomy 13 and 18 in the pregnancy. This test has an approximate 93% detection rate for Down syndrome and a 5% false positive. That means 5% of women who take this test will get an abnormal result, even when the baby does not have the condition. Abnormal hormone levels from the FTS may be associated with other pregnancy complications. A large nuchal lucency measurement may let us know there is an increased chance for other birth defects. FTS is a good first step in screening a low-risk population. The second type of testing is cell-free DNA, or CF DNA. This testing goes by many names, including cell-free DNA, CF DNA, non-invasive prenatal testing or NIPT, and non-invasive prenatal screening. Each lab calls their cell-free DNA something different, such as MaterniT21 and Panorama. CF DNA screening is a blood test. Instead of looking at hormones, though, this test looks at fragments or bits of DNA in your blood. These fragments are called CF DNA. It is normal for CF DNA to be in your blood. When a woman's blood is drawn during pregnancy, most of the CF DNA in her blood will be from her. Her blood will also contain CF DNA from the placenta. In most pregnancies, the placenta and the growing baby have the same chromosome makeup. While CF DNA screenings started as a screen for Down syndrome, this test has evolved rapidly and continues to grow and change. While different labs test for different conditions, CF DNA remains primarily a screen for common chromosome abnormalities. These include Down syndrome, trisomy 13, and trisomy 18, as well as sex chromosome changes. For the majority of laboratories performing CF DNA, the detection rate for Down syndrome is over 99% with a false positive rate of less than .1%. As a screen, CF DNA can miss affected pregnancies. CF DNA can call pregnancies abnormal, even when the baby does not have the chromosome abnormality. In some cases, a result cannot be obtained from CF DNA. This test is the most accurate screen for chromosome abnormalities in a pregnancy, but it does not screen for other things like the FTS test does. Screening may be right for you, if you wish to learn more about the health of your baby without taking any risk of miscarriage. For women who do not have a specific risk factor and who want general information about the pregnancy, hormonal screening such as the first trimester screen may be a good place to start. For women who have particular concerns regarding chromosome abnormalities, CF DNA is a more accurate test for these conditions. If a patient has an abnormal screening test, she has the option to undergo diagnostic testing for further information. If you wish to learn more about diagnostic testing, please watch the Diagnostic Testing in Pregnancy video.