Assessment of childbirth-related post traumatic stress disorder in Australian mothers: Psychometric properties of the City Birth Trauma Scale.

Background: The City Birth Trauma Scale (BiTS; Ayers, Wright & Thornton, 2018) is self-report measure of Post-Traumatic Stress Disorder (PTSD) symptoms following childbirth, based on DSM-5 criteria. We report on the first study of the psychometric properties of the BiTS in the Australian population.

Methods: Participants were mothers of infants aged 0-12 months (N = 705), who completed the BiTS and measures of related constructs. Confirmatory factor analysis was performed to assess the factor structure of the BiTS. Examination of the reliability, convergent, divergent and discriminant validity and acceptability of the BiTS was also examined.

Results: Confirmatory factor analysis supported a bi-factor model of Birth-related Symptoms (BRS) and General Symptoms (GS) of post-partum PTSD as well as a global CB-PTSD factor. Internal consistency was found for the BiTS total scale and two proposed subscales (BRS and GS). BiTS total scores were significantly associated with an established measure of PTSD, providing support for convergent validity. Evidence of discriminant validity was examined by comparing the BiTS to an established measure of postpartum depression.

Limitations: The present sample may over-represent participants with traumatic birth experiences in comparison to the general public. Furthermore, use of self-report measures limits the capacity to confirm the diagnostic status of participants.

Conclusion: These findings suggest that the BiTS is a valid and reliable measure of childbirth-related PTSD, suited for use in postpartum populations. Total scores on the measure may be informative for clinical and research purposes, while evidence suggests strong support for interpretation of subscale scores.