Prevalence and determinants of first-trimester gestational diabetes mellitus among high-risk pregnant women attending primary health centres in Puducherry, India: a cross-sectional study

Introduction: Gestational diabetes mellitus (GDM) is increasingly recognised as a public health challenge in India. Although screening is conventionally performed at 24-28 weeks of gestation, emerging evidence suggests that clinically relevant dysglycaemia may be present much earlier in pregnancy. However, data on first-trimester GDM from primary healthcare settings remain limited. This study estimated the prevalence of first-trimester GDM among high-risk pregnant women attending primary health centres in Puducherry, India, and identified associated sociodemographic, clinical and behavioural factors. Methods: We conducted a cross-sectional analysis of baseline data from 1505 pregnant women (<13 weeks' gestation) enrolled in a community-based cluster randomised controlled trial across 13 primary health centres. GDM was diagnosed using a one-step 75 g oral glucose tolerance test applying WHO 2013/International Association of Diabetes and Pregnancy Study Groups criteria. Prevalence ratios were estimated using modified Poisson regression with robust SEs, accounting for clustering at the primary health centre level. Results: The prevalence of first-trimester GDM was 15.1% (95% CI 13.4% to 17.0%). Maternal age >25 years, obesity, nulliparity and previous GDM were independently associated with higher GDM prevalence. In contrast, higher dietary adherence scores, adequate physical activity and energy intake below estimated requirements were also associated with higher GDM prevalence. Conclusions: Approximately one in six high-risk women attending public-sector primary health centres had GDM detected during the first trimester. These findings highlight a substantial early metabolic burden and support strengthening early screening and prevention strategies within primary healthcare systems in India.