Objective: The association between gestational diabetes mellitus (GDM), perinatal complications and long-term morbidity is gaining increased attention. However, the global burden of GDM and the existing responses are not fully understood. We aimed to assess country prevalence and to summarize practices related to GDM screening and management. Methods: Data on prevalence and country practices were obtained from a survey administered to diabetologists, obstetricians and others working on GDM in 173 countries. Results: GDM prevalence estimates range from <1% to 28%, with data derived from expert estimates, and single-site, multi-site and national prevalence assessments. Seventy-four percent of countries that completed the survey have national GDM guidelines or recommendations. Countries use a variety of screening approaches. In the countries where universal screening is recommended, the percentage of pregnant women screened ranges from 10% to >90%. Conclusions: We found large variations in estimated GDM prevalence, but direct comparison between countries is difficult due to different diagnostic strategies and subpopulations. Many countries do not perform systematic screening for GDM, and practices often diverge from guidelines. Countries need to carefully assess the cost and health impact of scaling up GDM screening and management in order to identify the best policy option for their population.