Routine Prenatal Screening Tests
Overview
The following routine genetic screening uses a blood test to safely check for certain genetic conditions.
These tests show if your pregnancy has a higher chance of being affected by certain conditions. They do not diagnose or tell you for sure if a condition is 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 a blood test 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 chromosomal differences.
NIPT is offered any time after 10 weeks of pregnancy.
If you have NIPT in the first trimester, you do not need other screening tests. You can also choose to have the NIPT later in pregnancy.
Results usually take between seven and 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 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 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 chance.
FTS is done between 11 weeks plus two days and 13 weeks plus three days of pregnancy. You will have 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. FTS uses the results along with your age to determine your screening result.
Typically, your health-care provider will share your screening results within seven to 10 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 an advanced diagnostic test to find out if your pregnancy truly is affected by these genetic conditions.
Learn more about first trimester combined screening from Prenatal Screening Ontario.
Second trimester screening (STS)
STS uses a blood test 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 first trimester screening.
You do not need to have this test if you already received a low-risk result from 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 an advanced diagnostic test to find out if your pregnancy truly is affected by these genetic conditions.
Learn more about second trimester screening from Prenatal Screening Ontario.