BACKGROUND AND PURPOSE:

• Harper et al. (AJOG, 2020) investigated whether early screening for GDM improves perinatal outcomes in obese women

METHODS:

• Randomized controlled trial (RCT)
• Participants
  • Obese women (BMI ≥30 kg/m2)
  • Exclusion criteria: Pre-existing diabetes | Major medical illness | Bariatric surgery | Prior cesarean delivery
• Exposures
  • Early screening at 14 to 20 weeks
  • Routine screening at 24 to 48 weeks
• Study design
  • 50-g, 1-hour glucose challenge test
  • Followed by 100-g, 3-hour glucose tolerance test if screen ≥135 mg/dL
• GDM diagnosed using Carpenter−Coustan criteria
  • If screen negative at 14 to 20 weeks, rescreened at 24 to 28 weeks
• Primary outcome
  • Composite: Macrosomia (>4000 g) | Primary cesarean delivery | Hypertensive disease of pregnancy | Shoulder dystocia | Neonatal hyperbilirubinemia | Neonatal hypoglycemia within 48 hours following delivery
• Sample size calculation
  • 58 women with gestational diabetes per group
  • 80% power with a 2-sided α of 0.05 to detect a 50% relative reduction in the incidence of the primary outcome
  • Sample size was reduced during interim analysis due to increased GDM baseline compared to original assumption (950 new total)

RESULTS:

• 922 women were randomized with full outcomes
  • Early screening: 49.8% (459 women)
  • Routing screening: 50.2% (463 women)
  • Baseline characteristics similar between groups
• Early screening group
  • GDM diagnosis: 15.0% (95% CI, 11.9 to 18.6%; 69 women)
    • <20 weeks: 6.3% (95% CI, 4.3 to 8.9%)
    • >24 weeks: 8.7% (95% CI, 6.3−11.7%)
• Routine screening group
  • GDM diagnosis: 12.1% (95% CI 9.3 to 15.4%; 56 women)
• Early screening did not reduce the incidence of the primary outcome (P=0.07)
  • Early screening: 56.9%
  • Routine screening: 50.8%
  • Relative risk 1.12 (95% CI, 0.99 to 1.26)

CONCLUSION:

• Early screening for gestational diabetes in obese women did not reduce the composite of perinatal adverse outcomes compared to routine screening
• Authors acknowledge that the study was powered to identify a large difference and smaller differences may not have been detected
• ACOG recommends screening women with BMI ≥25 kg/m2 and additional risk factors (see ‘Related ObG Entry’ for summary of ACOG GDM guidelines) and the authors suggest that future studies should focus on this cohort

Learn More – Primary Sources:

Early gestational diabetes screening in obese women: a randomized controlled trial

Related ObG Topics:

Updated ACOG Guidance on Gestational Diabetes

Screening for Gestational Diabetes: The ‘2 Step’ Approach

Does Metabolic Syndrome Contribute to a Longer Time to Pregnancy and Infertility, Independent of Obesity?

Does Ultrasound Early in Pregnancy Improve Fetal Cardiac Visualization in the Setting of Obesity?