Continuous Glycemic Exposure Over Oral Glucose Tolerance Test Thresholds for Hyperglycemia in Pregnancy: A Systematic Review and Phenotype-based International Consensus Implementation Blueprint Using Continuous Glucose Monitoring and Automated Insulin Delivery

Hyperglycemia in pregnancy has long been approached through dichotomous thresholds derived from the oral glucose tolerance test (OGTT), a strategy that brought diagnostic uniformity but has proven less capable of capturing biological variability, temporal glycemic dynamics, and downstream fetal risk. In parallel with evolving clinical practice, continuous glucose monitoring (CGM) has increasingly suggested that risk is more closely related to cumulative glycemic exposure than to isolated diagnostic values. Against this background, we conducted a systematic review, reported in accordance with Preferred Reporting Items for Systematic Reviews and Meta-Analyses 2020, to examine whether an exposure-based, phenotype-informed framework could better integrate emerging evidence and inform care. Searches were performed across major biomedical databases and supplemented by manual screening, with explicit eligibility criteria and transparent study selection procedures. Although not prospectively registered (e.g.,, PROSPERO), methodological steps were predefined and fully documented to enhance reproducibility. Thirty studies encompassing randomized trials, observational cohorts, and consensus reports were included. Given substantial heterogeneity in study design, CGM metrics, and outcome definitions, quantitative meta-analysis was not appropriate; instead, a structured narrative synthesis was undertaken. Across studies, CGM-derived parameters – particularly time-in-range, time-above-range, nocturnal dysglycemia, and glycemic variability – showed more consistent associations with fetal growth and neonatal outcomes than OGTT-based categories. Distinct exposure patterns emerged across clinically recognizable phenotypes, including early-onset dysglycemia and insulin-resistant or insulin-deficient gestational diabetes. However, variability in CGM definitions and reporting limited direct comparability across studies. We therefore propose a phenotype-stratified implementation framework linking exposure metrics with stepwise management, from lifestyle strategies to automated insulin delivery. These findings support a shift toward viewing hyperglycemia in pregnancy as a continuum of exposure, while highlighting the need for standardized CGM metrics and prospective validation.