Results
SEARCH RESULTS
The systematic search on 20/03/18 retrieved 602 quantitative studies from the five databases, and an additional seven studies from reference searching of appropriate reviews identified by the search (Figure 1) . After deduplication, 431 records remained for abstract screening. Of these, full text screening was carried out on 68, following which 11 quantitative studies were included (Table 1) . The updated search on 25/10/19 retrieved one more relevant quantitative study (Table 1) . The qualitative search on 20/03/18 retrieved 73 studies from the five databases. 17 qualitative studies were found in the quantitative search process and these added to the qualitative group (Figure 2) . After deduplication, 70 records remained for abstract screening. Full text analysis was performed on seven studies, of which two met the inclusion criteria (Table 2) . The updated search on 25/10/19 retrieved no new appropriate qualitative studies.
STUDY CHARACTERISTICS
The 12 quantitative studies were all observational; 10 were cohort and two were cross-sectional . Both qualitative studies presented findings from interviews. In the quantitative group, sample size ranged from 42 to 1842, with a mean of 464 participants. Sample sizes in the qualitative studies were much smaller, ranging from eight to 84. Three quantitative studies were conducted in Canada, two in England, two in Israel, two in Sweden, one in Australia, one in Germany and one in the USA. Both of the qualitative studies were from Sweden. Recruitment of participants for the studies was mostly through either community midwifery services or maternity wards in hospital, but one recruited participants through the internet and via maternity services and one recruited specialist midwives at clinics for postnatal PTSD .
While the qualitative studies used semi-structured interviews to collect data about the experiences of women with postnatal PTSD and those who supported them, the quantitative studies all used diagnostic tools to examine the prevalence of PTSD amongst their participants. Several diagnostic tools were used, with the most commonly used scales including the Post-traumatic Stress Diagnostic Scale , used by three studies and the Impact of Event Scale , also used in three studies .
QUALITY ASSESSMENT
The quality of the quantitative cohort studies was assessed using the NOS , which found all 10 of the cohort studies had a medium risk of bias. The cross-sectional studies were assessed using the CEBM checklist. One scored six out of a possible 12 desirable answers and the other scored five , indicating the studies may not be of high quality. The qualitative studies were assessed using the relevant CASP checklist . Both achieved a score of at least 8 out of 10, showing the studies were of good quality. Full quality assessments can be seen in