A prospective cohort study to refine gestational diabetes glycaemic surveillance targets

Guidance on threshold glucose values beyond which treatment intensification for GDM is warranted, is based on provider and consensus opinion due to a lack of high-quality evidence-based trials. We sought to determine the glucose levels above which dietary therapy alone should be considered insufficient. A prospective cohort study of women diagnosed with GDM after 24 weeks’ gestation was designed. Fasting and postprandial blood glucose was modelled using a random effects model to determine between-subject and within-subject variation. Logistic regression analysis was used to model blood glucose readings in excess of thresholds with pregnancy outcomes and optimal models were selected using the Akaike Information Criterion. Odds-ratios and p-values were reported for the selected best models. Data management and statistical analysis were performed using SAS Version 9.4. 43,703 glycaemic data points were available for analysis from 324 patients whose GDM was managed by dietary and lifestyle therapy alone, comprising 20,931 fasting and 22,772 postprandial readings. For composite perinatal outcome, the optimal criterion for fasting blood glucose was a fasting threshold above 99mg/dL on no more than 10% of occasions (OR=0.67,95% CI=0.94–2.38, p=0.091). The optimal criterion for postprandial glucose was an upper limit threshold of 137mg/dL exceeded on no more than 30% of occasions, reaching statistical significance (OR=4.94, 95% CI=1.54-15.9, p=0.007). Fasting hyperglycemia was associated with induction of labour but not with other clinical outcomes. In contrast, postprandial hyperglycemia was associated with induction of labour, preterm delivery, operative vaginal delivery, and adverse perinatal outcome. Intensification of treatment for GDM with supplemental hypoglycaemic agents is justified in patients exceeding a 1-hour postprandial threshold level of 137mg/dL on more than 30% of occasions. We have defined that this threshold may target those at risk of both a composite perinatal outcome and softer clinical outcomes such as operative delivery and neonatal hypoglycaemia.View Large Image Figure ViewerDownload Hi-res image Download (PPT)