The cross-sectional data presented in this article are part of the longitudinal “LABOR”-study (Longitudinal Analysis of Birth mode and Outcomes Related) in which three different groups of women were recruited: pregnant women, women who had their baby within the last 12 months, and women who had their baby more than 12 months ago. After their first assessment, all participants were asked if they were willing to take part in further follow-up assessments, scheduled at 3, 6, and 9 months after study entry. For the present study, only women of the second group, i.e., women who gave birth within the last 12 months were included. Exclusion criteria were death of the child during or after birth, younger age than 18 years, and insufficient German language skills. Invitations to take part in the study were posted on social media, such as Instagram and Facebook, as well as parents' blogs and forums between February and April 2020. The study was conducted online with the use of the platform EFS survey by QuestBack (unipark.de). Several arrangements ensured high quality of data. The platform offers the possibility to block participants from completing the questionnaire more than once. To ensure that participation was not only motivated by incentives like money or gift cards, women did not receive any kind of compensation. Since answers were obligatory for the participants, no imputation for missing values had to be conducted. Participants could complete the questionnaire on a smartphone or computer with an active internet connection in an environment of their choice. Participants were informed that some of the questions might relate to unpleasant or even traumatic experiences, which might trigger unwanted memories and emotions. Further, participants were informed about their right to withdraw from the study at any given time and were advised to seek professional help if needed (informed consent included a list of mental health services like the German National Suicide and Crisis Line). A total of 1,072 women who met inclusion criteria gave informed consent to follow the study protocol. Ethical approval was granted by the ethics committee of the Psychologische Hochschule Berlin (approval no. AZ: EK201921-II) and the study was performed in accordance with the Declaration of Helsinki. All data were stored anonymously and in accordance with the German General Data Protection Regulation (GDPR). On average, it took participants around 45 min to complete the whole assessment, including further questionnaires, which were not relevant for this study. Participants could pause and continue the questionnaire afterwards.

Exploratory factor analysis (EFA) on a random split-half sample (n = 536), calculations of correlation coefficients for convergent and divergent validity, and tests for group differences were performed using IBM SPSS statistics version 27 for windows. Univariate ANOVA with Bonferroni post-hoc comparisons were used to analyze potential differences regarding type of delivery. Confirmatory factor analysis (CFA) in the holdout sample (n = 536) was performed using IBM SPSS Amos version 27. Fit indices included Root Mean Square Error of Approximation (RMSEA), Standardized Root Mean Square Residual (SRMR), Comparative Fit Index (CFI), and Tucker-Lewis Index (TLI). Good (and adequate, respectively) model fit is indicated by RMSEA ≤ 0.06 (0.06–0.08), SRMR ≤ 0.08, and CFI as well as TLI ≥0.95 (0.90–0.95) (34).

A total of N = 1,072 mothers were included in the final sample (age: M = 30.6, SD = 4.7). Almost all women were in a permanent relationship. Most children were born by spontaneous vaginal birth (n = 739) and for approximately 60% of mothers it was their first birth. Only 5% of births took place before gestational week 37 (see Table 1 for further details).

Responses to the City BiTS in accordance with DSM-5 criteria for PTSD are shown in Table 2. About 22% women fulfilled the stressor criterion by indicating that they believed they or their baby would be seriously injured or even die during childbirth (or immediately afterwards). A total of 28 (2.6%) women fulfilled all criteria to qualify for a PTSD diagnosis according to DSM-5 criteria.

With a Kaiser-Meyer-Olkin coefficient of 0.92 and a chi-squared value of (χ² = 5336.06; df = 190; p < 0.001) in the Bartlett's test of sphericity, results indicated that the sample can be used for factor analysis (35, 36).

In accordance with previous validations of the City BiTS, an EFA using principal component analysis with varimax rotation was conducted (18, 21). Applying Kaiser's rule (retain Eigenvalues >1) and the screen test, a structure with two factors could be found. Factor 1 included items 3–12 and factor 2 included items 13–22. Items 23 and 24 were excluded from EFA, since they can be used to measure dissociative symptoms but do not represent main symptoms of PTSD. In our study, the total scale accounted for almost 52% of variance, with the subscales “Birth-related symptoms” and “General symptoms” explaining roughly 38 and 14% of the variance, respectively (see Table 3 for further details).

Based on theoretical reasoning and results of previous studies, the fit of three different models was tested in CFA. Firstly, we tested a model with four factors as determined in the diagnostic criteria of PTSD in the DSM-5, including the dimensions Intrusions (items 3–7), Avoidance (items 8 and 9), Negative cognitions/mood (items 10–16), and Hyperarousal (items 17–20). This analysis showed a poor fit of the model with four factors [χ(164)2 = 1288.86, χ²/df = 7.86, RMSEA = 0.113, SRMR = 0.093, CFI = 0.81, TLI = 0.78].

Secondly, we tested a model with one overall factor. This model also had to be rejected [χ(170)2 = 2050.71, χ²/df = 12.06, RMSEA = 0.144, SRMR = 0.119, CFI = 0.68, TLI = 0.64].

Thirdly, we tested a model with two factors that has previously been shown to yield an acceptable to good model fit. However, in one prior study minor modifications of the model (i.e., deletion of item 8) were necessary to reach acceptable model fit (18). In the current study, the two-factor model with two correlated dimensions in accordance with the original validation (“Birth-related symptoms” and “General symptoms”) was the best fit to the data according to all fit indices [χ(169)2 = 771.27, χ²/df = 4.56, RMSEA = 0.082, SRMR = 0.056, CFI = 0.90, TLI = 0.89]. Yet, the 90% confidence interval for the RMSEA (0.076−0.088) was slightly above the suggested cut-off of 0.08 (37). However, since items of the City BiTS aim to measure symptoms of childbirth-related PTSD according to DSM-5 we decided against deletion of items.

Analysis of the internal consistency by Cronbach's Alpha resulted in good to excellent reliability of 0.90 for the “Birth-related symptoms” subscale, 0.89 for the “General symptoms” subscale, as well as 0.92 for the total scale. Deletion of any of the items did not increase Cronbach's Alpha substantially.

Convergent and divergent validity were tested by correlating both subscales and the total scale of the City BiTS against the IES-R, PCL-5, EPDS, and the DASS-Anxiety subscale (see Table 4).

Univariate ANOVA was employed to assess if more invasive and medically complicated types of delivery lead to more severe symptoms of PTSD. Main effects could be found for the subscales “Birth-related symptoms” and “General symptoms” as well as the total scale (all p < 0.001; see Table 5; Figure 1). Bonferroni post-hoc comparisons revealed that for the subscale “Birth-related symptoms” scores differed statistically significantly between spontaneous vaginal birth and all other types of delivery (all p < 0.001). Furthermore, there was a statistically significant difference between elective and emergency CS (p = 0.02). The only statistically significant difference found for scores of the scale “General symptoms” was between the groups spontaneous vaginal delivery and emergency CS (p < 0.001). For the score of the total scale the post-hoc comparisons revealed that the group spontaneous vaginal delivery differed from all other groups (p < 0.01). Other group differences could not be found (all n.s.).

The study has noteworthy strengths such as the large sample size and the use of several different measures to establish convergent and divergent validity. Most notably, our translation of the City BiTS is the first German questionnaire, which offers the possibility to assess childbirth-related PTSD on the basis of DSM-5 diagnostic criteria. Therefore, standardized use of the German version of the City BiTS in postpartum women could improve perinatal healthcare fundamentally. Yet, there are also limitations that need to be acknowledged. Our results were obtained from cross-sectional data and preexisting symptoms of mental disorders were not assessed. Thus, we cannot determine whether women who already suffered from symptoms of PTSD or other mental disorders exhibit different scores on the City BiTS than women with no such history. Therefore, future research should apply longitudinal designs measuring symptoms of childbirth-related PTSD at several points in time to allow for an estimation of trajectories. This could facilitate early identification of women at risk to suffer from chronic childbirth-related symptoms of PTSD (4, 46–48). Further, even though the sample size was large, a selection bias cannot be ruled out. Web-based surveys offer easy accessibility, but women who use social media on a regular basis are more likely to be represented in online samples (49). Thus, further studies should aim to recruit more representative samples of women. Additionally, in our sample only a low percentage of women fulfilled DSM-5 diagnostic criteria for PTSD. Even though the results are similar to previous studies, subsequent validation studies should include populations at a comparably higher risk for childbirth-related PTSD (3, 4, 50). Additional efforts should be made to examine women belonging to different ethnic groups.

The findings of the present study provide strong evidence that the German version of the City BiTS offers adequate psychometric properties. This version is fit for use and perinatal healthcare might improve by its application in postpartum women. Furthermore, a questionnaire especially developed to assess childbirth-related PTSD will hopefully heighten the acceptance of standardized measurement of mental health in the peripartum period. Due to its explicit wording, women might relate more to a questionnaire on childbirth-related PTSD than to more general questionnaires assessing PTSD which might make their participation in postpartum psychological assessment more likely. As a result, childbirth-related PTSD might get more widely recognized by healthcare providers and affected women. In addition, efficient identification of women suffering from symptoms of childbirth-related PTSD will expedite allocation to adequate treatment for PTSD and might prevent them from being treated for e.g., postpartum depression instead. Based on this knowledge, evidence-based prevention and intervention strategies for childbirth-related PTSD can be refined in the future. In summary, the German version of the City BiTS may represent a useful tool in clinical routine and could help to make prevalence estimates of childbirth-related PTSD comparable across different countries.