Implications of changing the diagnostic criteria for gestational diabetes mellitus (CDC4G): a healthcare cost analysis alongside a stepped wedge cluster randomised trial

Objective: 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). Design: A cost-analysis alongside the Changing Diagnostic Criteria for Gestational Diabetes (CDC4G) randomised controlled trial. Setting: Sweden, with risk-factor based screening for GDM. Population: 47 080 pregnant women and their infants. Methods: 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. Main Outcome Measures: Estimated costs for obstetric surveillance (including GDM-management), delivery and neonatal healthcare until 28 days postpartum. Results: 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. Conclusions: 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.