BACKGROUND AND PURPOSE:

• Australia and New Zealand uses the ‘one step’ GDM screening approach, but adopted a higher glycemic threshold than the IADPSG recommendation
• Crowther et al. (NEJM, 2022) assessed whether the detection of gestational diabetes mellitus (GDM) using lower vs higher glycemic criteria would lead to lower perinatal morbidity

METHODS:

• Randomized trial
  • 2 district health boards in New Zealand
• Participants
  • Singleton pregnancy between 24 to 32 weeks
  • Had a 75-g oral glucose-tolerance test (OGTT) for GDM (‘one step’)
• Intervention
  • Lower glycemic criteria
    • Fasting plasma glucose level of at least 92 mg per deciliter (≥5.1 mmol per liter) or
    • A 1-hour level of at least 180 mg per deciliter (≥10.0 mmol per liter) or
    • A 2-hour level of at least 153 mg per deciliter (≥8.5 mmol per liter)
  • Higher glycemic criteria
    • Fasting plasma glucose level of at least 99 mg per deciliter (≥5.5 mmol per liter) or
    • A 2-hour level of at least 162 mg per deciliter (≥9.0 mmol per liter)
• Primary outcome
  • Large for gestational age (LGA) infant
    • Birth weight >90th percentile according to Fenton–WHO standards
• Secondary outcomes
  • Maternal and infant health

RESULTS:

• Lower glycemic criteria: 2022 women | Higher glycemic criteria: 2039
  • Infants born to women in the lower group: 2019
  • Infants born to women in the higher group: 2031
• GDM diagnoses were higher using lower glycemic criteria
  • Lower glycemic criteria: 15.3%
  • Higher glycemic criteria: 6.1%
• There was no significant difference in risk for LGA among lower vs higher glycemic criteria groups
  • Higher glycemic criteria: 8.8%
  • Lower glycemic criteria: 8.9%
  • Adjusted relative risk (aRR) 0.98 (95% CI, 0.80 to 1.19); P=0.82
• The following were more common in the lower glycemic criteria group
  • Use of health services
  • Use of pharmacologic agents
  • Neonatal hypoglycemia
• Maternal and infant health were generally similar between the two groups
• There was no differences in adverse effects between the groups
• Among the women in both groups who had glucose test results that fell between the lower and higher glycemic criteria
  • Those who were treated for GDM (195 women) benefitted and had fewer large for gestational age infants than those who were not treated (178 women)

CONCLUSION:

• Using lower GDM glycemic criteria (IADPSG) did not improve pregnancy outcomes or lower the risk of large for gestational age infants vs higher glycemic criteria (current Australia & New Zealand standard)
• The authors state

Two previous randomized trials have compared the IADPSG criteria with the Carpenter–Coustan screening criteria, but data from trials comparing the IADPSG criteria with the criteria currently recommended for use in New Zealand are lacking

Both previous trials showed that there were more women who received a diagnosis of gestational diabetes with the IADPSG criteria than with the Carpenter–Coustan screening criteria but that there was no improvement in perinatal health

Overall, the risks of giving birth to a large-for-gestational-age infant and of other infant or maternal complications were not lower with the lower glycemic criteria than with the higher glycemic criteria

Learn More – Primary Sources:

Lower versus Higher Glycemic Criteria for Diagnosis of Gestational Diabetes

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