Psychometric Properties of the Chinese Version of the Ford Insomnia Response to Stress Test (FIRST-C) Among Pregnant Women in Qinghai Province, China: A Cross-Sectional Validation Study with Measurement Invariance Testing.

PURPOSE: This study examines the psychometric properties and measurement invariance of the FIRST-C in a sample of pregnant women from Qinghai, with a particular focus on invariance across ethnic groups and between the second and third trimesters in this high-altitude, multi-ethnic region. METHODS: An 810-participant cross-sectional study using convenience sampling was conducted at a tertiary hospital in Qinghai from March to August 2025. Participants completed demographic and sleep questionnaires in paper or online format. Internal consistency was evaluated with Cronbach's alpha, construct validity with confirmatory factor analysis (CFA), and criterion-related validity by correlating FIRST-C scores with the Pittsburgh Sleep Quality Index (PSQI). Measurement invariance across ethnic groups and gestational stages was examined through multi-group CFA. RESULTS: The FIRST-C showed strong internal consistency (α = 0.917) and a unidimensional structure with good fit indices (χ2/df = 2.897, TLI=0.983, CFI=0.987, RMSEA=0.048, SRMR=0.018). Criterion-related validity was supported by a weak yet significant positive correlation with the Pittsburgh Sleep Quality Index (PSQI) (r = 0.22, p < 0.001), distinguishing trait-like reactivity from state-like quality. Employing a previously defined cut-off, 50.2% of participants surpassed the high sleep reactivity threshold. Multi-group confirmatory factor analysis (CFA) affirmed measurement invariance across ethnic groups and across the second and third trimesters. CONCLUSION: The FIRST-C demonstrates satisfactory psychometric properties and measurement invariance across ethnic groups and between the second and third trimesters in this Qinghai pregnancy sample, supporting its use as a research instrument for assessing sleep reactivity in this population.