427: When should early screening for gestational diabetes occur?

Objective: While ACOG and ADA recommend early screening for gestational diabetes (GDM) in overweight women with additional risk factors, the timing of “early” is poorly defined. We sought to define the optimal timing of early screening by comparing testing results and outcomes by the gestational age at screening. Study Design: Secondary analysis of a multicenter randomized controlled trial of obese women with singleton non-anomalous gestations comparing early to routine screening for GDM. Women were excluded for pregestational diabetes, major medical illness, bariatric surgery, or primary cesarean. All screening was accomplished with the two-step method: women with 1-hr glucose challenge test (GCT) ≥135 mg/dL underwent a 3-hr test with Carpenter-Coustan criteria for diagnosis. For this per protocol analysis, early screening was stratified into two-week blocks (14-15.9, 16-17.9, 18-18.9, and 20-21.9). Value of the GCT, proportion with GCT≥135 mg/dL, proportion with GDM, and incidence of the primary composite outcome (primary cesarean, macrosomia [>4000g], pregnancy induced hypertension, shoulder dystocia, hyperbilirubinemia, and hypoglycemia) were compared across strata. The composite outcome was compared between each early stratum and the routine screen group. Groups were compared with a chi-squared, chi-squared for trend, or Student’s t-test as appropriate. Results: Of 857 women, 390 (45.5%) received screening between 14-21.9 weeks. Strata were similar in age, race, BMI, and HbA1c. Women screened earlier were more likely to have hypertension (p=0.03). GCT value, GDM diagnosis < 24 weeks, and gestational age at diagnosis of GDM did not change by timing of early screen (Table 1). Incidence of the primary outcome did not change by timing of early screen. No timing of early screening was associated with a decrease in the primary composite outcome compared to routine screening (Figure 1). Conclusion: Between 14-21.9 weeks, timing of early GDM screen did not impact screening and diagnosis values, nor did it impact the effect of treatment at current screening and diagnosis thresholds. [Formula presented] [Formula presented]