BackgroundGestational diabetes mellitus (GDM) is characterized by hyperglycemia during pregnancy. There are many diabetes-specific tools for collecting information validated in Brazilian Portuguese. However, there are no specific instruments to assess knowledge about GDM in Brazilian Portuguese. The aim of this study was to cross-culturally adapt and validate the Brazilian Portuguese version of the Knowledge of Gestational Diabetes Mellitus questionnaire (GDMKQ).MethodsThis study was conducted in southern Brazil from January to December 2023. Women with GDM or diabetes identified during pregnancy were considered eligible based on specific criteria. Clinical and demographic data were obtained through a medical records search. The GDMKQ underwent a multistep adaptation process, including translation, back-translation, content validity assessment, and cognitive interviews. After administration to participants, internal consistency, item-total correlation, and intraclass correlation were assessed. Confirmatory factor analysis was also conducted to ensure validity.ResultsA total of 155 pregnant women were recruited for the study. Most participants were aged 18–30 years, and hypertension was the main comorbidity (25.2%). Regarding education, most participants (58.7%) attended high school. The Brazilian Portuguese version of the GDMKQ consisted of 32 items. The intraclass correlation was established by two independent interviews with 57 participants, yielding a correlation coefficient of 0.79 (p < 0.01). Internal consistency (Cronbach’s alpha) was 0.81 overall but was less than 0.7 for each domain. Item-total correlations were calculated, and confirmatory factor analysis indicated a good model fit. The final Brazilian Portuguese version of the questionnaire consisted of 32 items.ConclusionsThe Brazilian Portuguese version of the GDMKQ yielded a reliable and valid tool for evaluating diabetes knowledge in pregnant women.