Routine Prenatal Screening Tests
Overview
The following routine genetic screening tests use blood tests to safely screen for certain genetic conditions.
They can tell you if your pregnancy has a higher chance of being affected by certain conditions. These tests cannot diagnose or tell you for sure if the genetic conditions are present.
Please talk to your health-care provider to learn more about these tests.
Types of routine screening
Non-invasive prenatal testing (NIPT)
NIPT uses blood tests to help identify pregnancies with an increased chance of certain genetic conditions.
It is the most accurate screening test to help identify pregnancies with an increased chance of Down syndrome, trisomy 18 and other chromosome differences.
NIPT is offered any time after 10 weeks of pregnancy.
If you have the NIPT in the first trimester, you do not need to have other screening tests. However, you can also choose to have the NIPT later in your pregnancy.
Results usually take between seven to 10 business days. Your health-care provider will discuss what your results mean, including the chances of a false positive or a false negative.
If your results are positive, you may choose to have an advanced diagnostic test to find out if your pregnancy truly is affected by those genetic conditions.
Learn more about NIPT from Prenatal Screening Ontario.
First trimester combined screening (FTS)
FTS is a set of tests that is offered in the first trimester of pregnancy. It can identify pregnancies with an increased chance of Down syndrome, trisomy 13 or trisomy 18.
FTS combines your age, ultrasound measurements and blood test results to assess your chances.
The FTS is done between 11 weeks plus two days and 13 weeks plus three days of pregnancy. You will have both the ultrasound and the blood test on the same day.
The ultrasound is called a nuchal translucency (NT) ultrasound and the blood test measures the levels of two proteins in your blood. The FTS uses the results of these tests along with your age to determine your results.
Typically, you will receive the results from your screening test from your health-care provider within seven to 10 days after the test.
Your health-care provider will discuss what your results mean, including the chances of a false positive or a false negative.
If your results are positive, you may choose to have an advanced diagnostic test to find out if your pregnancy truly is affected by those genetic conditions.
Learn more about first trimester combined screening from Prenatal Screening Ontario.
Second trimester screening (STS)
STS uses blood tests to identify pregnancies with an increased chance of Down syndrome or trisomy 18.
You may choose to have this test if you did not have the first trimester screening.
You do not need to have this test if you have already received a low-risk result from the NIPT. It is also not recommended if you are pregnant with multiples (twins or more).
Results are usually sent to your health-care provider within five business days.
Your health-care provider will discuss what your results mean, including the chances of a false positive or a false negative.
If your results are positive, you may choose to have an advanced diagnostic test to find out if your pregnancy truly is affected by those genetic conditions.
Learn more about second trimester screening from Prenatal Screening Ontario.