In 2015, more than 90% of Australian antenatal care providers transitioned to the IADPSG recommendations for screening and diagnosing GDM. In the Australian state of Queensland, this resulted in 34% more women being diagnosed with GDM. Based on the increased number of women being treated for GDM, we hypothesized that perinatal outcomes, commonly associated with GDM, should decrease for pregnant women without GDM. We used routinely collected perinatal data of over 124,000 women to examine the difference in perinatal outcomes in the year before (2014) and after (2016) state-wide policy was changed for diagnosing GDM. Logistic regression was used to estimate the odds ratio and 95% confidence intervals for the risk of developing selected perinatal outcomes in women without GDM. Despite 34% more women being diagnosed and treated for GDM, there was a statistically significant increase in the year after the changes to the diagnostic criteria for women without GDM for: pregnancy-induced hypertension (OR 1.10, 95% CI 1.03 - 1.16), large-for-gestational (OR 1.37, 95% CI 1.17 - 1.60), small-for-gestational age infants (OR 1.75, 95% CI 1.59 - 1.92) and neonatal hypoglycaemia (OR 1.23, 95% CI 1.15 - 1.30). There was a decrease in respiratory distress (OR 0.93, 95% CI 0.88 - 0.98). Our results add to the growing body of evidence that changing diagnostic criteria has had little impact on outcomes for women GDM and in our study, the outcomes for women without GDM appeared to have worsened. Although our study design does not allow us to examine why this negative shift has occurred, we hypothesize that the additional resources required for treating women with GDM may have been provided at the expense of women without the condition. We question whether changing the diagnostic criteria was the correct choice for our population, given the increase in costs of treatment and recommend further research on potential harms in both the GDM and non-GDM populations.
N.J.L. Meloncelli: None. A.G. Barnett: None. S.J. de Jersey: None.