Co-Development and Content Validity of an Instrument to Collect Integratively the Social Determinants of Health in Postpartum Lactating People

Postpartum lactating people are particularly vulnerable to inequities in social determinants of health (SDH), yet no validated tool currently exists to assess these factors comprehensively. This study aimed to co-develop and establish the content validity of an instrument to integratively evaluate SDH in this population. Guided by the Mixed Methods Appraisal Tool, an interdisciplinary e-Delphi panel assessed item sufficiency, clarity, coherence, and relevance. Statistical analyses included the item-level (I-CVI) and scale-level (S-CVI/Ave) content validity indices, average agreement between experts (AABE), Fleiss’ kappa (κ), and Aiken’s V coefficient (V) (p < 0.05). Cognitive interviews were conducted with postpartum lactating participants representing diverse characteristics to assess interpretability. The initial version of the instrument included 135 items across nine sections addressing general demographics, education, employment, home environment, lifestyle, social support, healthcare access, stress, intimate partner violence, insomnia, and nutrition. Based on expert input, it was refined to 131 items through structural and lexical revisions. Content validity indices indicated strong agreement: I-CVI ranged from 0.66–1.00, S-CVI/Ave > 0.95, AABE > 14.26, and κ and V > 0.90. Final adjustments following cognitive interviews led to a 128-item version optimized for clarity and relevance. This instrument offers strong content validity for SDH assessment in postpartum lactating people and supports sustainable use in health research.