BACKGROUND

The objective of this study was to investigate whether an isolated abnormal 1-hour glucose challenge test (GCT) among patients without gestational diabetes (GDM) is associated with adverse outcomes.

METHODS

This is a retrospective cohort study of patients who underwent GDM screening at ≥ 24 weeks' gestation with a 1-hour GCT and delivered a singleton fetus at > 35 weeks' gestation at an urban tertiary hospital from 1/2013 to 10/2021. Data were extracted from an electronic medical record data warehouse using standardized billing/diagnosis codes. Individuals were categorized into 3 groups: normal screening (1-hour GCT value < 140 mg/dL), intermediate screening (1-hour GCT value ≥ 140 and < 200 but normal 3-hour glucose tolerance test (GTT)), and GDM (1-hour GCT ≥ 200 mg/dL or abnormal 3-hour GTT). The primary composite perinatal morbidity outcome included any of the following: large for gestational age (LGA) birthweight, birth injury, hypoglycemia with neonatal intensive care unit (NICU) admission, respiratory distress syndrome, transient tachypnea of the newborn, apnea, NICU admission, or perinatal death. Multiple secondary outcomes were also evaluated. Bivariable analyses and multivariable logistic regression modeling were performed.

RESULTS

Of 37,277 eligible patients, 29,698 (79.7%) had normal screening results, 5092 (13.7%) had intermediate screening results, and 2487 (6.6%) were diagnosed with GDM. There were significant differences in baseline characteristics between the three groups, including age, parity, race and ethnicity, payer-type, obesity, and pre-pregnancy metformin use. Compared to normal screening, intermediate screening was associated with an increased risk for the composite perinatal morbidity outcome (OR 1.23, 95% CI 1.15-1.32), cesarean (OR 1.37, 95% CI 1.28-1.46), and hypertensive disorders of pregnancy (OR 1.30, 95% CI 1.20-1.40). Associations for these outcomes were further pronounced in those with GDM compared to normal screening (OR 1.86, 95% CI 1.70-2.03; OR 1.69, 95% CI 1.56-1.84; and OR 1.57, 95% CI 1.42-1.74, respectively). After adjusting for potential confounders, increased risks for the composite perinatal morbidity outcome persisted for those with intermediate screening (aOR 1.18, 95% CI 1.10-1.26).

CONCLUSIONS

In addition to patients with GDM, individuals an isolated abnormal 1-hour GCT without GDM were also at increased risks for adverse pregnancy outcomes. Further investigation is needed to understand if patients with mild dysregulation may still benefit from other interventions.