Insights Into Glucose Variability Using Continuous Glucose Monitoring in Mothers With Gestational Diabetes Compared to Mothers at High Risk of Gestational Diabetes Who Have a Negative Oral Glucose Tolerance Test.

Gestational Diabetes (GDM) is associated with higher than normal blood sugar levels in pregnant women which has the potential to harm the baby and mother. The condition resolves with delivery of the baby, but during the pregnancy there is a limited time window for diagnosis and treatment before harm may be caused.

GDM is thought to affect up to 32% of pregnancies and is becoming more common due to rising rates of obesity and maternal age. The current recommended practice in the UK for the diagnosis of GDM is to use the oral glucose tolerance test (OGTT), which is two plasma blood glucose tests (one at baseline and one 2 hours after a glucose load) performed on expectant mothers who have at least one risk factor for GDM at 28 weeks gestation. This method is not standard internationally, with some countries using the test on all woman who fall pregnant, others adhering to different diagnostic thresholds, and others performing the test in a different way. Furthermore, there is no international consensus on the best way to diagnoses GDM. The challenge in diagnosing the condition arises because the results of the OGTT relies upon only two glucose measurements and therefore are not always accurate, meaning that some expectant mothers with GDM are missed, and others who do not have GDM are incorrectly told they have the condition.

Pregnant women who develop GDM but are not identified by the OGTT may suffer complications which could have been avoided with glucose lowering therapy, whilst woman who are incorrectly diagnosed with the condition may have their pregnancies unnecessarily medicalised, both of which places extra burden on the healthcare system. Therefore, improving the accuracy of the diagnosis of GDM has the potential to improve outcomes in pregnancies worldwide (and significantly impact upon current practice).

Recent technological advances in the field of diabetes care have seen the emergence of continuous glucose monitoring (CGM) - digital sensors placed on a patient's skin which constantly read the blood sugar level and communicate with their smart phone. Data from the CGM sensor is sent via Bluetooth to the smart phone, and using software downloaded in an app, is converted into a graphical summary illustration called an 'ambulatory glucose profile' (AGP) allowing for better treatment decisions to be made.

CGM devices are revolutionising the monitoring and treatment of diabetes, including GDM, however they are not utilised for diagnostic purposes. This study examines the challenging task of accurately diagnosing GDM by comparing the CGM data of patients with GDM with the CGM data of individuals at high risk of GDM (who are OGTT negative) to determine if the OGTT result is predictive of high blood glucose.