Descriptive statistics
Participants’ age ranged between 18.19 and 42.53 at the 24th week of gestation (mean age 30.60, SD = 4.43). Nulliparous women were somewhat younger than parous women (mean age = 29.40, SD = 4.42 for nulliparous; mean age = 31.95, SD = 4.04 for parous women; F (1, 1141) = 102.13, p < 0.01). Nulliparous women had a higher mean income than parous women, but the groups were similar in terms of marital status and education (Table 1).
Table 1 Mean ages and percentages of marital status, education and income according to parity (t test and χ
2 tests)
In general, nulliparous women tended to have higher PRAQ-R and PRAQ-R2 scores than parous women. The biggest difference between the groups could be observed in item 8, as expected. Item values and factor sum scores in factors 2 and 3 tended to increase during the study, but in factor 3, they tended to decrease. PRAQ-R2 correlations between weeks 24 and 34 were moderately strong, ranging from r = 0.47, p < 0.01, to r = 0.72, p < 0.01. For correlations across week 24 and week 34 items, see Table 2.
Table 2 Mean (SD) values of PRAQ-R2 items and total and factor sums, and statistical significances of differences between nulliparous and parous women (Mann–Whitney U test) and of changes during the study (Wilcoxon Signed Ranks test)
Reliability analysis
An overview of all Cronbach’s alphas for PRAQ-R and PRAQ-R2 across the total scale and the subscales, and across nulliparous and parous women, is presented in Table 3. PRAQ-R and PRAQ-R2 Cronbach’s alphas across the total scale were good (above 0.80) and generally comparable. Cronbach’s alphas for the subscale Fear of giving birth were good for the PRAQ-R2: 0.71 and 0.75 for parous women in week 24 and 34 respectively, and 0.79 and 0.75 for nulliparous women in week 24 and 34 respectively. For this subscale in PRAQ-R, Cronbach’s alphas were also good for nulliparous women: 0.78 for week 24 and 0.77 for week 34. However, for the parous women, Cronbach’s alphas were low: 0.40 for week 24 and 0.51 for week 34. Cronbach’s alphas for the subscales Worries about bearing a physically or mentally handicapped child and Concern about one’s own appearance were also good (above 0.77).
Table 3 Cronbach’s alphas across the old and new total scale and subscales, separately for nulliparous and parous women
Confirmatory factor analysis
Week 24
In week 24 data, CFA based on PRAQ-R2 showed that the three-factor model had an acceptable to good fit in both nulliparous and parous women (χ
2 (32) = 96.88, p < 0.01, CFI = 0.98, TLI = 0.97, RMSEA = 0.06 for nulliparous, and χ
2 (32) = 111.19, p < 0.01, CFI = 0.97, TLI = 0.96, RMSEA = 0.07 for parous women). Likewise, the three-factor model was fitted on the combined group of nulliparous and parous women, resulting in a good fit (χ
2 (32) =156.81, p < 0.01, CFI = 0.98, TLI = 0.97, RMSEA = 0.06). Standardized factor loadings are presented in Table 4.
Table 4 Standardized factor loadings of the PRAQ-R2 across the total sample of the three-factor model, for weeks 24 and 34 separately, and correlations between the items across week 24 and 34 for the total sample and parous and nulliparous women separately
Week 34
The three-factor model was also fitted to the 34-week data. For both nulliparous and parous women, CFA showed an acceptable to good fit to the data (χ
2 (32) = 114.28, p < 0.01, CFI = 0.97, TLI = 0.96, RMSEA = 0.07 for nulliparous, and χ
2 (32) = 118.39, p < 0.01, CFI = 0.97, TLI = 0.96, RMSEA = 0.07 for parous women). Likewise, the three-factor model was fitted on the combined group of nulliparous and parous women, resulting in a good fit (χ
2 (32) = 190.22, p < 0.01, CFI = 0.97, TLI = 0.96, RMSEA = 0.07). For standardized factor loadings, see Table 4.
Measurement invariance across nulliparous and parous women
Week 24
First, a baseline three-factor model was estimated in the week 24 data of PRAQ-R2 without any parous-invariance constraints. Model fit was overall acceptable, χ
2 (65) = 210.58, p < 0.01, CFI = 0.97, TLI = 0.96, RMSEA = 0.06. Second, factor loadings were constrained to be equal for nulliparous and parous women. The difference in χ
2 between the first model without constraints and this model with constrained factor loadings showed significant differences, χ2
diff (7) = 30.84, p < 0.01; however, the other three criteria indicated that invariant factor loadings did not result in a significantly worse fit, RDR = 0.077, ECVIdiff = 0.01, CI = 0.00–0.03, and ΔCFI = 0.005. In the next step, intercepts were constrained to be equal across groups. Again, χ2
diff was significant, χ2
diff (40) = 84.61, p < 0.01; however, the other criteria indicated that there were no differences between the model with constraint factor loadings only, and the model with constraint factor loadings and intercepts, RDR = 0.04, ECVIdiff = 0.00, CI = −0.02–0.03, and ΔCFI = 0.008.
Week 34
In the week 34 data of PRAQ-R2, the same procedure was used. A baseline three-factor model without any parous-invariance constraints was fitted, with an overall acceptable model fit, χ
2 (65) = 232.85, p < 0.01, CFI = 0.97, TLI = 0.96, RMSEA = 0.07. Second, factor loadings were constrained to be equal for nulliparous and parous women. There were significant differences in χ
2 between these models, χ2
diff (7) = 17.11, p < 0.01; however, the other three criteria indicated that invariant factor loadings did not result in a significantly worse fit, RDR = 0.05, ECVIdiff = 0.00, CI = −0.01–0.02, and ΔCFI = 0.002. Next, intercepts were constrained to be equal across groups. Again, χ2
diff was significant, χ2
diff (40) = 59.74, p < 0.01, while the other criteria indicated that there were no differences between the models, RDR = 0.03, ECVIdiff = −0.02, CI = −0.03–0.00, and ΔCFI = 0.004.