Effects of Changing Diagnostic Criteria for Gestational Diabetes Mellitus in Queensland, Australia

OBJECTIVE: To evaluate the effects of updated gestational diabetes mellitus (GDM) screening and diagnostic criteria on selected perinatal outcomes in Queensland, Australia. METHODS: This was a pre-post comparison study using perinatal data the year before (2014) and after (2016) the screening and diagnostic criteria for GDM was changed in Queensland, Australia. In 2015, Queensland adopted the one-step screening and diagnostic criteria based on the International Association of the Diabetes and Pregnancy Study Groups' recommendations. The data from 62,517 women in 2014 and 61,600 women in 2016 who gave birth from 24 weeks of gestation were analyzed in three groups in each year: women with GDM; women without diagnosed GDM; and total population. The outcome measures were gestational hypertension, cesarean birth, gestational age at delivery, birth weight, preterm delivery, large-for-gestational age (LGA) neonates, small-for-gestational-age (SGA) neonates, neonatal hypoglycemia, and respiratory distress. RESULTS: The diagnosis of GDM increased from 8.7% (n=5,462) to 11.9% (n=7,317). After changing the diagnostic criteria, the changes to outcomes, odds ratios (OR), and adjusted odds ratios (aOR) (95% CI) for outcomes with statistically significant differences for the total population were: gestational hypertension 4.6% vs 5.0%, OR 1.09 (1.03-1.15), aOR 1.07 (1.02-1.13); preterm birth 7.6% vs 8.0%, OR 1.05 (1.01-1.09), aOR 1.06 (1.02-1.10); neonatal hypoglycemia 5.3% vs 6.8%, OR 1.31 (1.25-1.37), aOR 1.32 (1.25-1.38); and respiratory distress 6.2% vs 6.0%, OR 0.96 (0.91-1.00), aOR 0.94 (0.89-0.99). There was no change to cesarean births or LGA or SGA neonates for women with or without diagnosed GDM or the total population. CONCLUSION: Except for a very small decrease in respiratory distress, changing the diagnostic criteria has resulted in more GDM diagnoses with no observed changes to measured perinatal outcomes for women with and without diagnosed GDM.