Pregnancy is a time of major change. One of the most common health issues that can appear during this time is Gestational Diabetes Mellitus (GDM). This condition is defined as a high level of sugar in the blood that is first discovered during pregnancy. It affects between 3% and 14% of pregnancies in Canada, and the numbers are rising.
Who is at Risk?
The risk factors for GDM are very similar to those for type 2 diabetes. People at highest risk:
- Are over the age of 35.
- Have a Body Mass Index (BMI) over 30.
- Have family members with type 2 diabetes.
- Belong to certain ethnic groups, including Indigenous, South Asian, Black or Hispanic backgrounds.
- Have a condition called Polycystic Ovary Syndrome (PCOS)
Testing and Diagnosis
All pregnant people are generally screened for GDM between the 24th and 28th week of pregnancy. However, people with several risk factors may be screened much earlier, and even in the first trimester.
There are two main ways to test for GDM:
- The Two-Step Approach: This starts with a “glucose challenge.” A pregnant woman drinks a sugary liquid at any time of the day, and blood sugar levels are checked one hour later. If the level is below 7.8, there is no GDM. If higher, then a 75-gram oral glucose tolerance test (OGTT) is done as described below.
- The One-Step Approach: The OGTT requires fasting for eight hours before the test, then drinking a sugary liquid. Blood sugars are then measured while fasting, after one hour, and again after two hours. The cut-off values for diagnosing GDM are slightly different if using a one-step or two-step approach. You only need one of the three levels to be above the threshold to diagnose Gestational Diabetes.
Finally, some women with GDM may have had undetected diabetes before pregnancy, that are discovered during the pregnancy using glucose levels or an A1C test.
Regardless of how it is diagnosed, catching GDM early is important because starting treatment, such as insulin or lifestyle changes, can improve health outcomes for both mother and baby.
About the author
Meera Luthra
MD, FRCP(C), Endocrinology and Metabolism, Professor of Medicine, McMaster University
articles
Glucose & Growth: Understanding Blood Sugar with Gestational Diabetes
How Your Body Changes During pregnancy, your body undergoes major shifts to fuel a growing baby. To ensure your child receives enough nutrients, your body naturally makes two key adjustments: It changes how it responds to insulin to increase glucose (sugar) in your blood. It modulates insulin levels to keep that blood sugar within a...
articles
Navigating Pregnancy with Type 1 Diabetes
Life with Diabetes and Pregnancy Managing type 1 diabetes during pregnancy is a lot of work, but it’s very doable. You’ll have frequent check-ups with a dedicated healthcare team, including an endocrinologist, diabetes nurse, and dietitian, who will provide continuous support. Having a strong support network of family, friends, and online groups can also make...
articles
Planning Pregnancy with Type 1 Diabetes
Planning for pregnancy when you have type 1 diabetes might seem overwhelming at first. It is very possible to have a healthy and safe pregnancy when living with type 1 diabetes. The most important thing is to plan ahead and work closely with your healthcare team in all stages of pregnancy and postpartum. Let’s take...