Background: Revised diagnostic criteria for gestational diabetes (GDM) in New Zealand on 75g oral glucose tolerance tests include lowering the fasting glucose (>5.5 to >5.3 mmol/L), adding a 1-h glucose (>10.6 mmol/L), and removing the 2-h glucose (>9.0 mmol/L). We assessed effects of these changes on demographics of those diagnosed and their perinatal outcomes.
Methods: Participants in the GEMS trial were grouped as meeting only the revised criteria (Additional group), only the current criteria so missed by the revised criteria (Missed group), both criteria (Both-Criteria group), and neither criteria (Non-GDM group).
Results: Among 3921 participants, GDM prevalence was 6.8% by the revised and 5.8% by current criteria (risk ratio 1.18, 95% CI 1.00 to 1.40). Women in the Additional (n=125) and Missed groups (n=83), compared to women in the Non-GDM group (n=3562), were more likely to be overweight/obese, have a family history of diabetes and be of Asian ethnicity. Women in the Additional-Treated group had less gestational weight gain but more induced labours compared to women without GDM, while their infants were born earlier, had lower birthweight, and more neonatal hypoglycaemia(all P<0ยท01). Compared to the Both-Criteria group (n=151), women in the Missed group had lower BMI, were less likely to be Pacific, required less pharmacotherapy, and experienced fewer postpartum haemorrhages.
Conclusions: Using the revised criteria will increase GDM diagnoses by identifying an additional high-risk group of women likely to benefit from treatment, although 35.5% of women currently treated for GDM will no longer be diagnosed, potentially compromising their health.