Skip to main content

What is first trimester screening for chromosomal abnormalities?

To determine the risk of certain chromosomal abnormalities, a combination of an ultrasound examination and a blood test can be done between 11 and 13 weeks of pregnancy.

This test, called a first trimester screening test for chromosomal abnormalities—or first trimester screening—combines a blood test and a nuchal translucency, which is an ultrasound that measures the skin on the back of the baby’s neck. The blood sample is analyzed for two chemicals, free Beta-hCG (human chorionic gonadotropin) and PAPP-A (pregnancy-associated plasma protein-A), which are normally found in the blood of all pregnant women. The results of the nuchal translucency and the blood test, when factored in with the mother’s age, give an estimated risk for major chromosomal abnormalities, such as Down syndrome or Trisomy 18. The measurement of the nuchal translucency is also linked to the risk for certain types of birth defects.

Our approach

Our experts understand that genetic testing during your pregnancy can be overwhelming and confusing—that’s why we take the time to fully explain the process and significance of each test. Together, we help you decide on the best course of action for you and your baby.

Why it's done

High-risk pregnancy—Some women may require extra monitoring, care or hospitalization during pregnancy. This may be due to a complication of pregnancy or another underlying medical need.

Pregnancy complications—There are many different types of pregnancy complications that can affect you, your baby or both. These complications range from common to rare, and can have a wide variety of causes and effects.

What to expect after treatment

The results of your first trimester screening will not be available for a few days. Once they are ready, you will receive a phone call with the results, revealing the likelihood of your baby having a chromosomal disorder.

First trimester screening does not give definitive answers, but does indicate the likelihood of a potential disorder. If the results suggest you are at an increased risk of having a child with a chromosomal disorder, your physician will walk you through the options and may recommend additional testing for confirmation.

Go to top