Lower vs Higher Glycemic Criteria for Diagnosing Gestational Diabetes: A Systematic Review and Meta-Analysis of Randomized Controlled Trials

Background: There is ongoing debate about the ideal blood glucose thresholds for the diagnosis of gestational diabetes mellitus (GDM), as individual randomized controlled trials (RCTs) comparing the lower International Association of Diabetes and Pregnancy Study Groups (IADPSG) blood glucose to criteria which use higher blood glucose thresholds have not been conclusive.<br><br>Objectives: This meta-analysis compared lower to higher blood glucose thresholds for GDM diagnosis in terms of GDM prevalence and adverse maternal and neonatal health outcomes.<br><br>Methods: We searched Cochrane CENTRAL, PubMed, Scopus, CINAHL, and preprint archives up to May 30, 2025, for RCTs that compared lower to higher glucose thresholds in the diagnosis of GDM in pregnancy. Endpoints were GDM prevalence and adverse pregnancy outcomes. After study quality assessment, meta-analysis was done using an inverse variance heterogeneity model, heterogeneity was assessed using I2, and publication bias by funnel plots. The quality effects model was used to synthesize evidence that was presented using forest plots.<br><br>Results: Ten RCTs, comparing IADPSG to higher blood glucose thresholds, with a total of 88,311 pregnant women, were included. After meta-analysis, the lower glycemic criteria compared to the higher glycemic criteria was associated with almost double the prevalence of GDM diagnosis (13.7% vs 8.04%, respectively) and the odds of GDM diagnosis (OR = 1.87, 95%CI 1.47-2.37, I2 = 93.4%), with moderate certainty GRADE evidence. For adverse pregnancy outcomes, the lower glycemic criteria compared to the higher glycemic criteria were associated with a trend towards lower odds for gestational hypertension (OR 0.57, 95%CI 0.30-1.07), and neonatal hypoglycemia (OR 0.35, 95%CI 0.06-1.93, I2=88.2%). However, there were no differences between the glycemic thresholds for cesarean section (OR 0.94, 95% 0.78-1.13, I2= 0%). For all the outcomes, there was low certainty GRADE evidence.<br><br>Conclusion: While the lower glycemic threshold results in close to double the prevalence of GDM and potentially higher workload for the healthcare system, this meta-analysis suggests that there may not be a difference in maternal and fetal outcomes when using lower vs higher thresholds in diagnosing GDM. However, the very low to low GRADE certainty suggests that further RCTs are needed to improve the certainty of evidence.