Secondary outcomes
Secondary outcomes included the impact of a history of postnatal PTSD on subsequent birth-planning. Research indicates that women who experienced a traumatic birth are more likely to request an elective caesarean section , so studies investigating this relationship were also evaluated. Another secondary outcome was how women with postnatal PTSD perceived the impact of social support on their mental health outcomes.
DATA ANALYSIS
The data from the quantitative studies were assessed for suitability in a meta-analysis. Studies were included if they reported a sample size, a mean PTSD score and standard deviation at a relevant follow-up point. Meta-analyses were conducted to explore the effect of mode of birth on the score of PTSD symptoms. Due to the range of scales used, it was necessary to convert each to standardised mean difference (SMD) using Hedge’s g as implemented in the Stata network suite of commands . When the reporting of subgroups differed, pooling was performed in line with recommendations from the Cochrane handbook . Results were interpreted using Cohen’s guidelines for interpretation of SMD magnitude : 0.2 a small difference, 0.5 a medium difference and 0.8 a large difference. Fixed effects models were used due to the small number of studies. Estimates were produced from both meta-analyses (considering only studies with directly relevant data) and network meta-analyses (which includes information from indirect comparisons when estimating the effect of interest). Heterogeneity was assessed through a comparison of the study characteristics. I2 could not be calculated.
Qualitative studies and quantitative studies not suitable for statistical analysis were reported narratively.