Healthy Pregnancy Guide Banner Image

Prenatal Tests

Throughout your pregnancy, a variety of tests are available. Some are routine tests (done during most all pregnancies to ensure you and your baby are healthy) while others are done by choice to screen for genetic conditions or done if a health care provider is concerned about your or your baby’s health. Speak to your health care provider to learn more about these types of tests and if they are right for you and your family.

The tests below marked with a * are routine tests done during pregnancy.


First Trimester Tests

Dating Ultrasound (Before 12 weeks)*
An ultrasound uses sound waves to see your baby. This ultrasound will measure how big the baby is to be able to confirm your due date. Women may not have this done if they opt for Enhanced First Trimester Screening (see below).

Enhanced First Trimester Screening (eFTS) (11-13 weeks)

This involves an ultrasound and a blood test to screen for potential genetic conditions such as Down Syndrome. Some people choose to have this done to allow for earlier decision-making about further testing and care. The ultrasound must be done before the blood work, but they don’t have to be done on the same day. For more information see: Enhanced First Trimester Screening (eFTS)

Non-Invasive Prenatal Testing (NIPT) is another simple blood test which can be used to screen for genetic conditions. It can be done after 9 weeks but you must meet certain criteria, or it will not be covered by OHIP. See here for more information: Non-Invasive Prenatal Testing

Chorionic Villus Sampling (CVS) (11-14 weeks)

If needed, a tube or a needle can be used to remove a sample of placenta to diagnose some genetic conditions. This is only done if one of the screening tests above is positive.


Second Trimester Tests

Maternal Serum Screen (14 to 21 weeks)

If you do not have the Enhanced First Trimester screen, a blood test to screen for genetic conditions can still be done during your second trimester.

Amniocentesis (After 15 weeks)

If needed, a tube or a needle can be used to remove a small amount of amniotic fluid to diagnose some genetic conditions. This is only done if an above screening test is positive.

Anatomy Scan (20 weeks)*

An ultrasound is performed to check the baby’s size, overall anatomy, location of the placenta, and the amount of amniotic fluid. You may be able to learn your baby’s gender at this appointment, so tell the technician if you want to know or not!

Glucose Screening (Glucose Challenge Test) (24-28 weeks)*
You will be given a sugary drink and after an hour your blood will be drawn. If positive, this may indicate that you have gestational diabetes.


Third Trimester Tests

Group B Streptococcus Test (GBS) (35-37 weeks)*

For this test, a sample is taken by swabbing the inside of your vagina and your rectum. If positive, you will be given antibiotics during labour. GBS is a common bacteria found in many women but if a baby comes into contact with it during a vaginal birth it can cause a serious infection in the baby.

Rh Immune Globulin (28-32 weeks)
Your blood type will be determined during early pregnancy. A person either has a positive blood type (Rh+) or a negative blood type (Rh-). If you are Rh-, you will be given a needle containing Rh immune globulin during pregnancy. This is to prevent your blood from reacting with your baby’s blood if your baby’s blood type is Rh+. Rh immune globulin is also given after major bleeding in pregnancy and after birth if your baby is Rh+. It prevents problems in future pregnancies.

Non-Stress Test (After 28 weeks)

If your health care provider is ever concerned about your baby’s well-being towards the later part of your pregnancy, they may send you to the hospital to have a Non-Stress Test (NST). For this test, you will have two elastic belts placed around your abdomen and a nurse will attach a monitor to each belt. One monitor will record the baby’s heart rate and the other monitor will record your contractions (if any). The test is usually 20 minutes long.


As always, speak to your health care provider about any questions or concerns you have about any prenatal tests.

For more information about tests that screen for genetic conditions see Prenatal Screening Ontario.

The PRHC also has a Genetics program where you can meet with a genetic counsellor to discuss your prenatal screening options, a positive screen, or a genetic condition in your family history.

back button to navigate back to previous page next button to navigate to next page