Predicting Dysglycemia in Individuals With Gestational Diabetes Immediately Postpartum Using Continuous Glucose Monitoring

Gestational diabetes is one of the most common medical disorders in pregnancy and affects up to 18% of pregnancies. It is associated with an increased risk of both maternal and neonatal complications. Importantly, gestational diabetes is a major risk factor for the postpartum development of pre-diabetes or type 2 diabetes (together referred to as dysglycemia). Specifically, half of people with gestational diabetes will develop dysglycemia within 10 years of delivery. Despite the high risk of developing dysglycemia, 50-80% of women with recent gestational diabetes are not receiving testing within a year postpartum.

There are likely many factors contributing to this low screening rate. These include individual factors such as socioeconomic status and maternal age, as well as the nature of the guideline recommended test itself. The Diabetes Canada 2018 Clinical Practice Guidelines recommend screening for maternal dysglycemia between "6 weeks to 6 months postpartum" with a 75g oral glucose tolerance test (OGTT). This recommendation is based on expert opinion. While the 75g OGTT is thought to be the "gold-standard" for screening for dysglycemia postpartum, it has many pitfalls. First, the OGTT is widely disliked by women as it is time consuming and inconvenient. It requires consuming a sugary drink in addition to two separate venipunctures. Second, the 75g OGTT is notoriously unreproducible. Finally, it takes only a "snap shot" of a woman's glucose and insulin response with only two measurements over two-hours.

Emerging technologies are changing the landscape of diabetes care. Continuous glucose monitoring (Freestyle Libre 2) is one such technology. People easily insert a small cannula just under the skin using an applicator. While the device is in place, it measures interstitial glucose concentrations every 15 minutes. It is a small disc (~size of a quarter) and it can be worn during typical daily activities such as sleeping, showering, and exercising. The sensor can store up to 8 hours of glucose readings in 15-minute intervals. People scan the sensor using a smartphone or reader to upload glucose readings to the Freestyle Libre 2 app, which can be viewed by a clinician and/or researcher. Continuous glucose monitoring gives a detailed picture of glycemic excursions throughout the day including both fasting and postprandial states.

There are currently no published studies examining the use of continuous glucose monitoring postpartum. Furthermore, no studies have examined continuous glucose monitoring's potential role in diagnosis of maternal dysglycemia postpartum. There is an unmet need to improve postpartum screening for individuals with gestational diabetes so that high risk individuals do not miss the opportunity for early treatment. To address this, the investigators will perform a study examining the use of continuous glucose monitoring immediately postpartum to estimate the risk of maternal dysglycemia postpartum. This is an observational study which aims to see if CGM can be used to diagnose diabetes. The CGM device in this study will be used for diagnosis and not as an intervention.

Inclusion criteria

• Pregnant individuals age 18 and older
• Diagnosed with gestational diabetes by the Diabetes Canada guidelines (including both the preferred or alternate testing approaches) or have an HbA1c of 6.0-6.4% during pregnancy
• Have any of the following: have an elevated fasting glucose (≥ 5.3 mmol/L) on the diagnostic 75g OGTT in pregnancy; required insulin or metformin for treatment during pregnancy; body mass index (BMI) ≥ 25kg/m^2, yes/no (<27 weeks gestation BMI of ≥25 kg/m^2 or ≥27 weeks gestation predicted BMI of ≥ 25 kg/m^2 using (current weight in kg - 10kg)/height in meters^2)
• Planned in-hospital delivery
• Able to provide informed consent
• Willingness to use the study device and complete assessments postpartum
• Have access to email in order to complete participant questionnaire through REDCap

Exclusion criteria

• A clinical diagnosis of non-gestational diabetes (i.e., pre-existing type 1 or 2 diabetes) prior to or during pregnancy
• Planned x-ray, MRI or CT within 3 weeks postpartum
• Has an implantable medical device (ex. pacemaker)
• On medications known to affect glucose metabolism (for example glucocorticoids, metformin etc.) while wearing the CGM postpartum
• On medications which may interfere with the Freestyle Libre 2 accuracy (for example Vitamin C >1000mg/day) while wearing the CGM postpartum
• Unable to speak and understand French or English
• Unable to consent or declined informed consent