Participants and procedures
Participants for an online study were recruited via social media posts and websites targeted at pregnant women, flyers and advertisement in gynecological and midwife practices and magazines, as well as word of mouth and snowballing techniques. Recruitment took place between April and October 2018. Women interested in participating in the study followed a link to an online survey platform where they were offered detailed information about the study, including its aims, confidentiality and inclusion criteria with the option to download study information material. A provision of informed consent was necessary for the complete online-survey to open. Informed consent was provided by agreeing to several consent questions including, for example, information on data confidentiality, on how to contact the researcher, and the voluntary nature of study participation. If interested women disagreed on any of the consent questions, they could not proceed to the online survey. Participating women could voluntarily take part in a lottery with a chance of winning one out of 10 parents’ guidebooks as incentive after completing the online survey. Inclusion criteria were a) age ≥ 18 years, b) current pregnancy ≥ 4 week’s gestation, c) sufficient German language skills to take part in the online survey, and d) informed consent.
Measures
Participants were asked to provide demographic and pregnancy-related variables, including age, marital status, household income, education, parity, weeks’ gestation as well as body height and pre-pregnancy body weight to calculate pre-pregnancy Body Mass Index (BMI = body weight (kg)/(body height (m))2).
Body image in pregnancy scale
The English-language original version of the BIPS [4] consists of 36 items to be answered on a 5-point response scale. Scale reference points differ depending on the aspect of body image measured (e.g. body image dissatisfaction, body image importance). The items cover seven factors: ‘preoccupation with physical appearance’ (six items), ‘dissatisfaction with facial features’ (four items), ‘sexual attractiveness’ (six items), ‘prioritizing appearance over body functioning’ (five items), ‘appearance-related behavioral avoidance’ (three items), and ‘dissatisfaction with body parts’ (six items). The past week prior to the assessment was chosen as the time referent, so that the women should think of their current pregnancy and weeks’ gestation while responding the items. Mean scores (range 1–5) are calculated for every subscale with higher scores indicating greater body image disturbance.
The BIPS items were translated adhering to a stepwise forward-backward translation rationale [26]. In a first step BIPS items were translated forward from English into German language independently by two native German-speaking study members. In a second step, translations were reviewed and discussed in the study team and a preliminary German version was approved. Ambiguities were resolved with the help of the author of the original English version. Then (step 3) a native English-speaker translated this preliminary version into English. In a last fourth step, the back-translated version was reviewed and compared with the English original version by the study team and the original author. Discrepancies were resolved by discussion and a first final German version of the BIPS (BIPS-G) was approved. Cognitive interviews based on thinking aloud and retrospective verbal probing techniques using this first German version were conducted with five pregnant women (mean age: 28.60; SD = 0.80; mean gestational week: 29.40; SD = 8.66) to evaluate the comprehensibility of the translated items. Overall, the comprehensibility and relevance of the items was good. Results from the cognitive interviews were used to slightly revise formulations of a small number of items (see Additional file 1 for the final BIPS-G version; the English-language original version of the BIPS is published in Watson et al. [4]).
Related constructs
Body dissatisfaction was measured using the German version of the Body Shape Questionnaire (BSQ; [27], [‘Fragebogen zum Figurbewusstsein’, FFB; [28]). The FFB total score ranges from 34 to 204 with higher scores indicating higher body dissatisfaction. The reliability, factorial and convergent validity of the FFB have been shown previously [29]. The reliability of the FFB sum score in the present sample was α = .97. Depression was assessed using the German version of the Edinburgh Postnatal Depression Scale (EPDS, [27, 30]). The EPDS sum score ranges from 0 to 30 with higher scores indicating a higher severity of depressive symptomatology. The German version of the EPDS has been shown to have a good reliability [30] and the applicability of the EPDS for the use during pregnancy has been established [31]. In our sample, the reliability of the EPDS sum score was α = .88. Anxiety was measured using the German version of the General Anxiety-7 Screener (GAD-7; [32, 33]). The GAD-7 sum score ranges from 0 to 21 with higher scores indicating more severe anxiety symptom levels. There is evidence for the reliability and validity of the German version of the GAD-7 in the general population [33]. The internal consistency of the GAD-7 sum score in the present study was α = .85. Self-esteem was measured with the revised German version of the 10-item Rosenberg Self-Esteem Scale (RSE; 34). The RSE sum score ranges from 0 to 30 with higher scores indicating higher self-esteem. The reliability and validity of the German version of the RSE has been established [34, 35]. The reliability of the RSE sum score in the present sample was α = .92. Eating disorder psychopathology was measured using the German version of the Eating Disorder Examination-Questionnaire (EDE-Q; [36, 37]). Twenty-two items cover the subscales restraint, eating concern, weight concern and shape concern. Subscale means and a mean Global Score indicating the overall eating disorder psychopathology were calculated. The German version of the EDE-Q has been shown to have a good internal consistency on Global Score and subscale level [38]. The reliability in the present sample was .78 ≤ α ≤ .93 for the EDE-Q subscales. The reliability of the Global Score was α = .95.
Statistical analyses
All statistical analyses were conducted using SPSS 25. The significance level was set to α = .05.
Item analyses
Standard item analyses were calculated including item mean scores and standard deviations, item difficulties (%) [pi = ((x̅i – min (xi))/(max (xi)-min (xi))*100 with x̅i = mean of item i; min (xi) = minimal value on item i; max (xi) = maximum value on item i] and corrected item-total correlations. Item difficulties range from 0 to 100%. Higher item difficulties indicate a higher agreement to the items, i.e. the higher the item difficulty the higher the probability of body image disturbances on the respective item.
Factor structure
Due to the novelty of the BIPS and the fact that the factor structure of the English original version of the measure has only been established in one study based on exploratory factor analysis thus far [4], we chose an exploratory over a confirmatory approach to test the factor structure of the newly developed German version. Following the procedure described in Watson et al. [4] a principal axis factor analysis (PAF) with oblique rotation (PROMAX) was performed on the 36 translated BIPS items. Factors were assumed to correlate as they all measure different aspects of pregnancy body image. Items with poor factor loadings on their primary factor (< .40) or high cross-loadings (difference of less than .20) were deleted. Extraction criteria were eigenvalues > 1 (Kaiser-Guttman criterion), visual inspection of the scree-plot, and the minimum average partial test (MAP test; [39]). The MAP test was performed following the procedure described by O’Connor [40]. In a second step, a second PAF was conducted using the number of factors extracted in the first analysis.
Reliability
The internal consistency of the final item set was calculated using Cronbach’s α. Mean inter-item correlations were calculated to inform about subscale homogeneity.
Validity
Convergent validity was assessed by calculating Pearson’s correlations between BIPS subscales and theoretically related constructs, including body dissatisfaction (FFB), depression (EPDS), anxiety (GAD-7), global self-esteem (RSE), and eating disorder symptomatology (EDE-Q). Multiple hierarchical linear regression analyses were conducted to test the incremental validity of the BIPS. Therefore, depression, anxiety, self-esteem and the EDE-Q Global Score of eating disorder psychopathology were separately regressed onto the BIPS subscales (third step) after controlling for body dissatisfaction (FFB, second step) and sociodemographic characteristics (BMI, age, household income).