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Department of Family and Community Medicine and St. Michael’s Academic Family Health Team

Pregnancy - Tests during pregnancy

At some point during your first few visits with your pregnancy provider you will begin the regular testing which is done during any pregnancy in Ontario. All of these tests are, of course, voluntary and are free under OHIP. They are offered to all pregnant mothers because they pick up problems we may not notice on exam and may not be felt you. They are a way to make your pregnancy and your baby healthier and safer.

During your first few visits

Screening for infections

HIV, gonorrhea, chlamydia, syphilis, hepatitis B and possibly hepatitis C may all be tested to try to protect the growing baby from these infections. We will also check that you are immune to (cannot be infected by) common infections that can be dangerous to the developing fetus or the pregnant mom: rubella, possibly hepatitis B and chickenpox. Finally, we will check for urine infections so we can treat them before they spread which is more common in pregnancy.

Making sure you’re healthy

It’s important to check for thyroid disease, anemia (low blood), vitamin B12 deficiency or abnormal cervix cells (PAP). All of these conditions can be treated if needed, to keep you healthier during pregnancy.

Your blood type

We always test your blood type. Everyone knows that there are different blood types (A, B, O or AB) but few know that for each of these types there is a POSITIVE and NEGATIVE state (i.e. A positive or A negative). Regardless of your lettered blood type, if you are NEGATIVE status there are some special treatments for you while you’re pregnant. You will need specific injections to ensure that your blood does not react to the baby’s blood. This is necessary if you ever bleed during your pregnancy, if you have certain procedures (ex. therapeutic abortions), at approximately 28 weeks of gestation, and after delivery. This injection contains antibodies to the POSITIVE component of blood typing which will glue onto the baby’s blood if he/she is POSITIVE status. These antibodies effectively hide the baby’s POSITIVE status and make sure that your blood will not react against the baby’s blood.

Before these injections were invented, some mothers with NEGATIVE blood would become ‘immune’ to babies with POSITIVE blood and not be able to carry such a pregnancy to term ever again. So It is very important to be treated in order to prevent future miscarriages.

Non-stress test

This test involves going to the hospital and having a probe on the belly which monitors the baby’s heart and uterine contractions for 20-40 minutes. It is done in all sorts of situations to check that the baby is well. This test is rarely done before 28 weeks of pregnancy. Someone from our team will explain both the reason for doing this test as well as the result as it applies to your particular situation.

Fetal biophysical profile

This is another test which is used in similar situations as the non-stress test. This time, the baby is watched on ultrasound and specific factors are looked at to assess baby’s well-being (ex. movements, fluid volume). Again, there are lots of reasons for ordering this test, and the interpretation of what the results may mean are different. Your provider will answer questions around why it is being done and what the results mean in your individual situation.

Glucose tolerance test + gestational diabetes

Higher blood sugars in pregnancy can happen just like in Type 2 diabetes. The higher sugar changes the pregnancy by changing the placenta as well as how the baby develops. These changes can harm the baby, the mother and the upcoming labour. So, it is important to notice diabetes in pregnancy and to treat the sugars so we can stop these changes.

The glucose tolerance test is performed between the 25th and 28th week of gestation. It is a NON FASTING test which takes an hour to finish. You will go to the lab, drink a container of sweet juice (called the “glucose challenge”) and an hour later have a blood test. If this test is abnormal you will do the main diabetes test which is a FASTING test (nothing to eat or drink except water for eight hours prior). You will go to the lab and have a blood test, drink a larger sweet juice bottle, and have blood tests one and two hours later. If this set of testing is abnormal it means you have gestational diabetes and will be referred for treatment by your provider.

Group B streptococcus test

GBS is a type of bacteria that can grow on the around your vagina and bum. It usually just lives there peacefully and, apart from the rare urine infection, does not harm you. During vaginal delivery your baby passes through the vagina and gets coated with bacteria from the surrounding areas. This is for the most part a protective process, during which the skin of the baby gets filled with ‘friendly’ bugs and is made unavailable for ‘unfriendly’ bugs who are more likely to cause infection. When GBS is on your skin, it also can be transferred onto the baby. Most babies who end up with GBS on their skin are fine, without any infections. A very few of these unfortunately do get infections from GBS and, when this occurs, the infection can be dangerous (even life-threatening).

At around 36 weeks of pregnancy, we will do a swab of your vagina and anus. If we find this bug to be growing there, we will give you antibiotics during labour (through the IV) and kill GBS before it gets onto your baby. Since doctors have started doing this, the number of sick newborns with GBS infections decreased and less babies die from GBS.

Immunizations in pregnancy

Vaccines, if they can safely be avoided, usually are in pregnancy. For this reason, it is ideal to have a pre-conception (pre-pregnancy) visit with your doctor or nurse practitioner, where the following vaccines can be discussed:

  • tetanus, pertussis, chickenpox/varicella, rubella (given as the MMR or mumps, measles, rubella vaccine), and influenza

While you’re pregnant, it is important to protect yourself and your baby from getting the flu.  This is why we advise all our patients (especially pregnant moms) to get their flu shots at the beginning of each flu season.  We also suggest having a pertussis (“whooping cough”) booster in your third trimester and this will be reviewed in detail with you when you reach this stage.  Finally, if you or your baby is travelling early in life to a hepatitis B endemic country we recommend vaccinating yourself and your baby after birth.

Keep in mind that vaccinations and vaccine schedules are an ever-changing part of medical care. Advice on immunizations during, and outside of, pregnancy changes quickly and your provider can explain any new recommendations if they apply.

Genetic screening

There are a few different types of genetic tests which are time-sensitive (meaning they have to be done at specific times during the pregnancy). They try to tell us the risk of the fetus having certain genetic problems: such as Down syndrome and spina bifida. These tests are called: first trimester screening, integrated prenatal screening, maternal serum screening or the non-invasive prenatal testing. The best explanation of these tests is on the Mount Sinai Hospital website. Please refer to the link below:

Screening counsellors

Prenatal Diagnosis Program
Mt. Sinai Hospital
700 University Avenue - Hydro Building, Toronto, ON M5G 1Z5
416-586-4946