Implications of Changing the Diagnostic Criteria for Gestational Diabetes Mellitus (CDC4G): A Healthcare Cost Analysis Alongside a Stepped Wedge Cluster Randomised Trial

To estimate the effect on healthcare resource use after introducing the World Health Organization diagnostic criteria (WHO-2013) for gestational diabetes mellitus (GDM) compared to former criteria in Sweden (SWE-GDM). A cost-analysis alongside the Changing Diagnostic Criteria for Gestational Diabetes (CDC4G) randomised controlled trial. Sweden, with risk-factor based screening for GDM. 47 080 pregnant women and their infants. A register-based cost-analysis from a healthcare perspective alongside a stepped-wedge cluster RCT of switching from SWE-GDM to WHO-2013 criteria in 2018. Analyses were made on the population level and repeated in the subgroup affected by the intervention, that is, those with plasma glucose values between SWE-GDM and WHO-2013 criteria. Sensitivity analysis by bootstrapping was performed. Estimated costs for obstetric surveillance (including GDM-management), delivery and neonatal healthcare until 28 days postpartum. On a population level, the WHO-2013 criteria were associated with increased costs of obstetric surveillance (adjusted mean [bootstrap confidence interval]) €94.0 [24.5-169.1], delivery care €20.4 [-33.5 to 75.4] and neonatal care €331.0 [75.1-589.0] per pregnancy, and in the affected subgroup €606.9 [377.7-872.4], €348.5 [126.0-542.0] and €129.3 [-559.0 to 980.9] respectively. Implementation of the WHO-2013 criteria in Sweden was associated with increased costs for obstetric surveillance and delivery on a population level, driven by the affected subgroup. The increased costs for neonatal care were associated with large uncertainty. A detailed understanding of the changes in resource use can guide decisions to mitigate cost increases.