Development and Validation of Breastfeeding Knowledge Test for Women with Gestational Diabetes Mellitus

Background/Objectives: Gestational diabetes mellitus (GDM) affects approximately 12.7% of pregnant women in South Korea. While breastfeeding provides critical health benefits for mothers with GDM and their infants, including improved insulin resistance and reduced Type 2 diabetes risk, no validated GDM-specific breastfeeding knowledge instrument exists. This study aimed to develop and validate a breastfeeding knowledge instrument for women with GDM. Methods: This methodological study employed systematic procedures for the development and validation of knowledge test. Initial item generation yielded 30 items across three domains: postpartum physical characteristics, breastfeeding barriers, and breastfeeding benefits. Content validity was evaluated by six clinical experts and ten experiential experts (women with GDM). An online survey was conducted in October 2022 with 220 women diagnosed with GDM who were either pregnant or within six months postpartum. Item analysis, exploratory factor analysis, and reliability testing were performed. Convergent validity was assessed by calculating the Pearson correlation coefficient with an established breastfeeding knowledge scale. Results: Following expert review and psychometric analysis, the final instrument comprised 14 items across three factors: postpartum physical characteristics (3 items), breastfeeding barriers (2 items), and breastfeeding benefits (9 items). The Kaiser–Meyer–Olkin measure was 0.884, Bartlett’s test was significant (χ2 = 838.835, p < 0.001), and factor loadings were satisfactory. The KR-20 reliability coefficient was 0.826, and criterion validity was confirmed. Conclusions: This first validated GDM-specific breastfeeding knowledge instrument enables the identification of knowledge gaps and the development of targeted educational interventions to improve maternal-child health outcomes.