Prenatal Tests

Routine early pregnancy blood tests

Early in your pregnancy, we will perform a set of routine blood test. These tests check a number of markers, including your iron levels, blood type, and screen for infectious diseases that can impact your baby.  

Rh Negative blood screening

We will check your blood type early in your pregnancy. A "negative" blood type means your blood does not have the Rh protein. If this is the case, you will be scheduled to have an injection called RhoGAM at 28 weeks of your pregnancy.

The RhoGAM injection ensures that you do not develop antibodies that might cause a reaction against a baby with an Rh positive blood type. RhoGAM offers important protection with very minor side effects.

A RhoGAM injection may also be needed if you have any bleeding during your pregnancy.

The RhoGAM injection is given in the Obstetrical Day Unit (ODU) on the 15th floor at Mount Sinai Hospital. Before you receive the injection, a blood test will be completed.  

If you experience bleeding from the vagina at any point during your pregnancy, please  let a member of your health care team know as soon as possible. 

Ultrasounds

There are several ultrasound appointments during your pregnancy. These appointments usually take place at either Mount Sinai Hospital or Women’s College Hospital.  The radiology departments of our two hospitals are affiliated.  

Dating ultrasound (approximately 8 weeks) 

We usually order an ultrasound around 7-9 weeks to confirm your due date, and to make sure the pregnancy is developing normally.

Nuchal translucency ultrasound (approximately 12 weeks)  

A nuchal translucency ultrasound measures the amount of fluid behind the fetus' neck. This ultrasound can provide information about certain genetic conditions and other health information about the baby.

Anatomy ultrasound (approximately 19 to 20 weeks)

The anatomy ultrasound examines the development of your baby's organs and makes sure your baby is developing properly.

In some cases, not all anatomical parts are clearly visible because of the position the baby is in. In these cases you may be called back to complete the anatomy scan on another day.

If you would like to find out the sex of your baby, please let the sonographer know before the scan.  

The anatomy scan can take several hours to complete, so please plan your day accordingly and bring water and a snack.  

Third trimester ultrasound (approximately 35 weeks)

You may have a final ultrasound to monitor your baby's growth and development. This ultrasound is booked by our office.  

An additional ultrasound may be required if you are pregnant beyond your due date. If you deliver your baby, this appointment is automatically cancelled.  

GBS infection screening

Between 36 and 38 weeks gestation, we screen all pregnant patients for Group B Streptococcus (GBS) bacteria. GBS bacteria is a common bacterium that can be found in the vagina, rectum or bladder.  Most patients who test positive for GBS do not have symptoms.

GBS can be passed on to a baby during a vaginal birth. A baby infected with GBS bacteria may become seriously ill. If you test positive for GBS, you will receive antibiotics during your labour to help prevent the GBS infection from spreading to your baby.  Please ensure your health care team is aware of any allergies to antibiotics.

Please visit the Society of Obstetricians and Gynaecologists of Canada for more information on GBS infection in pregnancy. 

Prenatal Genetic Screening 

Prenatal genetic screening tests estimate the chance of your baby having trisomy 18 (Edwards syndrome) or trisomy 21 (Down syndrome). These are two genetic conditions that can cause various health challenges including intellectual disability.  

Some families choose not to do these tests. We will discuss with you whether you feel that doing these tests is right for you. If you choose to undergo genetic screening during your pregnancy, there are a number of tests that you can choose from.

Learn more about routine prenatal screening tests.

If your screening tests are positive, you will be offered an appointment with the Prenatal Genetics Clinic where they will discuss additional tests with you, including amniocentesis and chorionic villus sampling.  

For more information visit Prenatal Screening Ontario.  

Gestational diabetes screening 

Gestational diabetes happens when your body cannot make enough insulin during pregnancy, even though you did not have diabetes before getting pregnant.  

It is important to manage gestational diabetes during pregnancy because it can affect your health and that of your baby.

Managing your blood sugar and regular monitoring of your baby's growth can help you have a healthy pregnancy and delivery.

Tests for gestational diabetes are usually done between 24 and 28 weeks of pregnancy using a glucose challenge test. If the results show you have high blood sugar levels, a glucose tolerance test is necessary to confirm the result.

Glucose challenge test: For this test you will be asked to drink a sugary liquid. After one hour, we will take a blood sample to measure your blood sugar levels.  

Glucose tolerance test: For this test your blood sugar is first measured after an overnight fast. During your appointment you will be instructed to drink a sugary liquid. Your blood sugar level is then tested one and two hours after drinking the liquid.