Prenatal Screening - Common Tests During Your Third Trimester
As you prepare for the arrival of your newest family member, there will be much to do but your most important priority continues to be your health and your baby’s health. At this stage in your pregnancy – as your due date gets closer – your prenatal checkups will double in frequency. Until now you will typically have visited your health care provider (doctor, midwife or other health care professional) for checkups on a monthly basis. As of week twenty-eight, these checkups will increase to approximately every two weeks, and will become weekly from week thirty-six.1 This prenatal care monitors your baby’s progress in order to identify any potential health risks early before they can become a problem for you or your baby. It helps mothers have healthier babies and ensures that everything is as it should be.
During third trimester checkups, much that occurs will be familiar as you will have experienced it in earlier checkups. Your blood pressure and weight will continue to be checked, as will your baby’s heart rate. Your abdomen will continue to be measured to monitor your baby’s growth. There will also be medical exams and screening tests that may be less familiar, as they are particular to this stage of your pregnancy. If your caregiver suggests certain tests, ask lots of questions because knowing what is involved is the best way to ease your mind and cope with any worries you may have. Questions and worries are as normal as the happy anticipation you feel, and are part of your journey into motherhood. By becoming a partner with your health care provider, you can rest assured that during this exciting time, you are doing what is best for your baby and for you.
We have detailed some of the more common tests so that you know what you may encounter in your prenatal checkups during this stage.
Biophysical Profile (BPP). This is an ultrasound exam that may be accompanied by a “Nonstress Test.” The BPP looks at your baby’s breathing, movement, muscle tone, heart rate and the amount of amniotic fluid (amniotic fluid index) to determine your baby’s well-being.2 It is a simple test that may be given in high-risk pregnancies to determine if the baby should be delivered earlier than planned, or it may be given if you have gone past your due date.
Nonstress Test (NST). This test is often part of the Biophysical Profile (BPP), and looks at your baby’s heart rate to movement reaction.3 It checks for signs of fetal distress, including lack of oxygen. You will either sit or lie down and fetal monitoring equipment, such as a belt placed around your abdomen, will be used. You may be asked to press a button whenever your baby moves, so that heart rate can be measured in conjunction with your baby’s movement. If your baby is asleep at the onset of the test it may be necessary for your health care provider to wake baby up with a loud noise, or you may be asked to ingest a sugary or carbonated drink to wake your baby up. This test may be given anytime in the third trimester and is often given when the mother goes past her expected delivery date.
Glucose Challenge Screening. This test typically takes place between weeks twenty-six and twenty-eight and is used to determine your risk of diabetes during pregnancy (known as gestational diabetes). You will be given a sugary-tasting drink that contains glucose, and an hour later a blood sample is taken to see how efficiently the glucose was processed. A positive result does not mean a diagnosis of diabetes – and in fact up to one quarter of women tested show elevated blood sugar – it simply means that more testing, such as the Gestational Diabetes Test, is necessary.
Gestational Diabetes Test.4 Typically performed between twenty-six to twenty-eight weeks to diagnose gestational diabetes mellitus (GDM). You will be asked to fast before this test, at which point a blood sample will be taken to measure the level of sugar in your blood, known as the baseline test. You will then be asked to drink a sweet solution and blood samples are taken to see how efficiently your body processes the glucose in the drink. If elevated blood sugar levels persist, it may mean that you are not producing enough insulin to regulate the amount of sugar in your blood. This may not effect you at all during pregnancy, but it could effect your baby.
Statistics vary but according to the Canadian Diabetes Association approximately 3.7% to 18% of women are diagnosed with GDM.5 It is a very treatable condition, managed primarily through diet modification and physical activity. Daily blood glucose testing and insulin injections may also be prescribed. Treatment lowers the risk of a caesarean section delivery, and it can help your baby avoid poor health. Gestational diabetes typically disappears upon delivery of the baby.
Group B Streptococcus (GBS). This routine screening may take place between weeks thirty-five to thirty-seven. It checks for common bacteria in the mother that are generally not harmful for her, but could be passed to the newborn during childbirth.6 Without preventative treatment these bacteria could pose health risks, such as pneumonia or infection, in a newborn. Treatment typically involves intravenous antibiotics during delivery.