A total of 67 people were recruited from maternity units and social media to take part in the study. They first completed an online questionnaire, then filled out the CityBiTS measure, and finally took part in a diagnostic interview over the phone. The CityBiTS scores were compared to the results of the interviews using ROC curve analysis. We looked at how well the scores identified cases (sensitivity), correctly identified non-cases (specificity), and overall accuracy to find the best cutoff scores and see how these compared to other available methods.

Inclusion Criteria:

• age 18 or more
• who had given birth with a minimum at four weeks prior to completing CityBiTS,
• who had a sufficient level of Swedish to participate.

Exclusion Criteria:

• Cases of stillbirth

Recruitment was performed from a risk group of individuals with a higher likelihood of having BR-PTSD than the average population, to decrease the number of needed diagnostic interviews. Recruitment was made achieved via two different paths. Since birth complications are important risk factors for BR-PTSD, individuals with documented medical complications during birth were recruited from nine birth units in different parts of Sweden for the first path. These were identified by the following diagnostic codes in medical records. Those meeting inclusion criteria were invited by postal mail, including information about the study as well as a link and QR-code to the first survey. The second recruitment path was via social media. The ad invited those who had recently given birth and experienced the birth as difficult.