**Background:** Exclusive breastfeeding (EBF) for the first six months of life is recommended by the WHO and UNICEF, yet global EBF rates remain low at approximately 38%, with European rates around 25% and Spanish rates varying from 16.8% to 39% depending on data sources. Previous studies using generic health literacy instruments (e.g., SAHLSA, NVS) found associations between health literacy and EBF duration, but these relationships were not determinant, likely due to the lack of specificity. Health literacy is a multidimensional construct encompassing access, understanding, appraisal, and application of health information. No validated instrument existed specifically for breastfeeding literacy (BFL). This study aimed to design and validate the first specific BFL instrument for perinatal women.
**Methods:** The study was conducted from December 1, 2021, to September 30, 2022, in three hospitals in the Valencian Community, Spain: Hospital Universitario de La Ribera, Hospital General de Castellón, and Hospital Lluís Alcanyís de Xàtiva. The instrument was developed based on Sørensen et al.'s integrated model of health literacy, organized into four dimensions: Access, Understand, Appraise, and Apply. Content validity was assessed by a panel of nine experts (midwives, lactation consultants, research nurses) across two rounds. The first round achieved an average congruence percentage (ACP) of 0.864; after revisions, the second round achieved an ACP of 0.913. The Content Validity Index (S-CVI/Ave) was 0.912. The initial version contained 28 items. For psychometric testing, a non-probabilistic convenience sample of 204 postpartum women was recruited. Inclusion criteria: having given birth in a participating hospital and voluntary consent. Exclusion criteria: linguistic barriers, multiple gestations, or neonatal admission to a neonatal care unit. Sample size was based on recommendations of 5–10 participants per item (minimum 140–280) and a minimum of 200 participants for questionnaire quality assessment. Construct validity was assessed using exploratory factor analysis (EFA) with principal axis factorization and oblique (ProMax) rotation. Internal consistency was measured using McDonald's Omega. Cluster analysis (k-means, two groups) determined cut-off points for inadequate vs. adequate BFL.
**Key Results:** Two items (Access6 and Appraise6) were removed due to poor factor loadings (<0.4), yielding a final 26-item instrument. The KMO test (0.924) and Bartlett's Test of Sphericity (X² = 3119.861; p ≤ 0.001) confirmed EFA feasibility. Four factors explained 60.54% of total variance: Factor 1 (Access) explained 44.02% (5 items), Factor 2 (Apply) explained 8.04% (7 items), Factor 3 (Appraise) explained 4.38% (9 items), and Factor 4 (Understand) explained 4.09% (5 items). Overall reliability was excellent (ω = 0.949), with dimension-specific values: Access ω = 0.809, Understand ω = 0.810, Appraise ω = 0.912, Apply ω = 0.873. All inter-dimension correlations were good to strong and statistically significant. The sample (n = 204) had a mean maternal age of 32.8 years (SD = 5.143; 95% CI 32.09–33.51); 45.59% delivered at HULR; 83.8% were Spanish-born; 50.5% had university education; 85.3% reported medium socioeconomic status. At discharge, 74% chose EBF, 6.4% mixed breastfeeding, and 19.6% formula feeding. Among primiparous women, 72.7% chose EBF. Of women opting for EBF, 82.3% had no doubts about feeding type during gestation. Among women with previous breastfeeding experience (n = 82), 52.4% perceived it as very good, 45.3% felt fully supported by healthcare professionals, and 63.4% had breastfed exclusively for six months or more. Cluster analysis showed the Understand dimension had the lowest proportion of women with adequate BFL (54.9%, n = 112), while Apply had the highest (66.2%, n = 135). Statistically significant associations: higher perceived socioeconomic status correlated with adequate Access BFL (p = 0.016); women choosing EBF had higher rates of adequate Understand BFL (59.6%, p = 0.023) and adequate Apply BFL (70.9%, p = 0.026); primiparous women had lower adequate Appraise BFL (p = 0.022); multiparous women of second gestation had the highest adequate Appraise BFL (78.9%, p = 0.018) and adequate Apply BFL (77.5%). No significant association was found between educational level and BFL in any dimension.
**Clinical Implications:** The BLAI is the first validated instrument specifically designed to measure breastfeeding literacy, addressing a critical gap identified in prior research where generic health literacy tools lacked specificity. The instrument can identify which competencies (access, understanding, appraisal, or application) individual women need to strengthen, enabling targeted antenatal and postnatal education. The finding that the Understand dimension had the lowest proportion of women with adequate BFL (54.9%) suggests that many women struggle to reflect on whether they truly comprehend breastfeeding information, highlighting an area for clinical focus. The Access dimension explained the most variance (44.02%), indicating that information access is a foundational competency. The lack of association between educational level and BFL suggests that breastfeeding literacy is a distinct construct not merely reflecting general education. The BLAI may be useful for evaluating the effectiveness of breastfeeding education programs and antenatal interventions. Future studies should conduct confirmatory factor analysis with larger samples, assess test-retest reliability, study convergent validity against a gold standard (once available), and explore the instrument's ability to predict EBF duration at six months. Adaptation and validation for health science professionals and students are also recommended. Limitations include the inability to study convergent validity (no gold standard existed), convenience sampling, and the need for more robust dimensionality analyses.