To Örebro University

Hyperglycaemia during pregnancy is one of the most common complicationsof pregnancy. In 2013, the World Health Organisation recommended diagnostic criteria (WHO-2013) for gestational diabetes mellitus (GDM), whichremains controversial due to an expected increase in prevalence, and the uncertainty as to the clinical relevance of treating these additional women or its cost-effectiveness.

Paper I involves a cross-sectional study of 4 918 pregnant women using riskfactor screening, which was poorly predictive of the WHO-2013 criteria, with an area under the curve of 40% (95% CI 24–32). In Paper II, a systematic review and meta-analysis of the prevalence of GDM according to the WHO2013 criteria in 136 705 women showed a 75% (RR 1.75, 95% CI 1.53-2.01) increased prevalence compared to the other GDM criteria. In Papers III-IV, a national stepped wedge cluster randomised controlled trial of 26 160 pregnancies before and 28 509 after the implementation of the WHO-2013 criteria across eight clusters during 2018 led to a 2.90 fold increase in GDM prevalence. No significant decrease was seen in the primary outcome, large for gestational age (LGA). There were, however, health benefits in secondary outcomes for the mother and neonate. There was a significant decrease in LGA dependent on the definition used, including the clinically used in Sweden (>2SD) with adjusted OR of 0.89 (95% CI 0.82-0.97). In Paper IV, the WHO2013 criteria led to increased resource use and incremental costs (€341.1 (195.9)) per pregnancy. The cost-effectiveness needs to be related to health benefits for the mother and/or neonate.

In conclusion, the current screening methods for GDM are in need of revision considering their poor predictive characteristics in finding GDM according to the WHO-2013 criteria. Implementing the WHO-2013 criteria in Sweden resulted in higher GDM prevalence with short-term increased resource use with uncertainty in costs savings and considerable healthcare benefits for the mother and neonate. This thesis provides evidence regarding the consequences of implementing the WHO-2013 criteria compared to former Swedish GDM criteria and may assist future decision-making.