The global prevalence of hyperglycaemia in pregnancy (HIP) is rising alongside increases in the prevalence of obesity and diabetes. The IDF estimates that 19.7% of live births in 2024 were affected, with 79% of cases due to gestational diabetes mellitus (GDM) and 20% due to overt diabetes in pregnancy and pre-existing diabetes in pregnancy combined. HIP is linked to complications for both mother and child, including long-term health risks. Significant ethnic and geographical variations exist in the prevalence and outcomes of HIP, with women from South Asia being at the highest risk of GDM. Variations in prevalence of HIP exist both between regions (e.g. 13.8% in Africa compared with 31.8% in South-East Asia) and within individual countries. Social determinants of health, such as healthcare access and delivery, economic stability, discrimination, migration, lifestyle and other sociocultural factors, along with environmental, biological and genetic factors, contribute to these ethnic differences. Geography impacts risk through factors such as seasonality, pollution and rurality. Further variation occurs due to substantial diversity in national approaches to screening and diagnostic criteria. Ethnic disparities in GDM outcomes include variations in complications such as preeclampsia and preterm delivery. To address these disparities, a standardised and cost-effective approach to GDM screening and diagnosis that reflects the ethnic diversity in glucose profiles is recommended. Locally tailored, national prevention strategies for those with prior GDM should be introduced as a matter of urgency. Furthermore, each country should implement tailored HIP management policies and guidelines that include strategies to address the ethnic, geographical and social disparities in outcomes.