Screening and Diagnostic Testing

During pregnancy, your caregiver will periodically request and run different tests both for you and your little one. These tests are designed to ensure that you are healthy and that your little one is progressing as she should.

Some of these tests include prenatal screening testing around 11-14 weeks. While not mandatory, these screening tests can help identify any problems with the developing fetus.

• Nuchal Translucency (NT) — This test is designed to help detect the possibility of Down Syndrome and is performed between 11-14 weeks. This non-invasive test is performed using an ultrasound to measure the depth and amount of fluid present under the skin behind the fetus's neck. This test is usually offered to every pregnant woman, so you can ask for it if it isn't.

• Serum Screening — Serum screenings are blood tests that look for substances in your blood that can predict your baby's risk of having Down Syndrome, other chromosomal abnormalities, or neural tube defects. Usually performed between 14 and 16 weeks, these types of tests do not provide definitive answers but only offer probabilities. An abnormal test result does not mean your baby has an abnormality; it only means you are at greater risk and may want to consider further testing.

• Integrated Screening — This is a combination of tests that look for indicators of Down Syndrome, Edward Syndrome, and neural tube defects. This screening has a lower false-positive rate than other kinds of screenings. This testing is a two-stage test that includes blood tests and an ultrasound. Testing occurs between 10-13 weeks for stage one and 15-16 weeks for stage two.

• One Stop Clinics for Assessment of Risk (OSCAR) — OSCAR occurs between 11-14 weeks and includes the NT scan and blood tests for free B-hcg and PAPP-A to determine the risk of abnormalities. The results are usually available within a few hours, which gives parents time to arrange more invasive testing.

• Chorionic Villus Sampling (CVS) — This diagnostic test is performed between 11-13 weeks. This test includes taking a tissue sample from the placenta since the baby and the placenta develop from the same cells. Most parents who choose CVS want to exclude Down Syndrome or other gene disorders like Thalassemia and sickle cell anemia. This test is invasive, so there are some things to consider before having it. Approximately 1 % of women who have this test will miscarry. There is also evidence that doing the test early could lead to an abnormality in limb growth. Last, the placenta contains mosaic cells that could suggest an abnormality when none is present.

Reference Sources

1. American Pregnancy Association - Chorionic Villus Sampling: CVS

2. WebMD - First Trimester Screening (Nuchal Translucency and Blood Test)

3. NCBI - One stop clinic for assessment of risk for fetal anomalies: a report of the first year of prospective screening for chromosomal anomalies in the first trimester