Objectives Gestational diabetes mellitus (GDM) carries significant feto-maternal risks. While early diagnosis and treatment effectively mitigate these adverse outcomes, the most effective strategy for screening and detection remains a subject of ongoing debate. Methods A secondary analysis of data from a large trial involving 35,430 women was conducted to estimate the proportion of GDM cases missed by targeted screening, compare maternal and neonatal outcomes between identified and potentially overlooked pregnancies, and identify maternal risk factors most strongly associated with adverse pregnancy outcomes using multivariable logistic and least absolute shrinkage and selection operator (LASSO) regression analyses. Results Approximately 11% of women not recommended for testing under a risk factor–based targeted screening strategy would have remained undiagnosed. The full 11-factor model and the simplified three-factor LASSO model, comprising increasing maternal age, obesity, and prior GDM, showed comparable predictive performance. Women with both GDM and maternal risk factors had the highest likelihood of adverse outcomes, whereas women with GDM but without maternal risk factors had lower complication rates than non-GDM women with maternal risk factors. Conclusion A simplified three-factor screening model demonstrated acceptable predictive performance and may provide a practical alternative in resource-limited settings. Furthermore, the coexistence of GDM and maternal risk factors was associated with increased clinical vulnerability, highlighting the need for closer surveillance and targeted management of these pregnancies.