Gestational diabetes mellitus (GDM) is an increasing cause of morbidity in women and their offspring. Screening and intervention can reduce perinatal and most likely also long-term diabetes consequences. There have been many economic studies, but not recently systematically compared. We conducted a systematic search and abstraction of cost-effectiveness and cost-utility studies from 2002 to 2014. We standardized all findings to 2014 US dollars. We found that cost-effectiveness ratios varied widely. Most variation was found to be due to differences in geographic setting, diagnostic criteria and intervention approaches, and outcomes (e.g., inclusion or exclusion of long-term type 2 diabetes risk and associated costs). We concluded that incorporation of long-term benefits of GDM screening and treatment has huge impact on cost-effectiveness estimates. Based on the large methodological heterogeneity and varying results in the existing body of evidence, we find it unreasonable to outline any global recommendations. For future economic studies, we recommend inclusion of long-term outcomes and adaptation to local preferences, as well as examination of the impact of the diagnostic criteria recently proposed by the International Association of Diabetes in Pregnancy Study Groups (IADPSG).