Methods
ELIGIBILITY CRITERIA
This review included both quantitative and qualitative studies to give a holistic overview of the literature. Studies from 1990 onwards were included, as research into PTSD following childbirth first started in this decade . This review included studies which explored PTSD in women who gave birth by different modes of birth as described in the introduction.
For quantitative research, studies were included if participants included women who had given birth within 6 months prior to recruitment to a live singleton infant carried to term in high-income countries as classified by the World Bank . Qualitative studies were included if participants were either postnatal women who met the criteria as above, or people who supported these women. This category included husbands or partners, friends, family, peers, support groups and healthcare providers.
SEARCH STRATEGY
The protocol for this review was registered on the PROSPERO International Prospective Register of Systematic Reviews (CRD42018089132). Searches were conducted in CINAHL, the Cochrane Library, MEDLINE, PsycINFO and Scopus on the 20thMarch 2018, and an update search was performed on the 25th October 2019. There were two searches run in each database: one for quantitative studies and one for qualitative studies. Reference searching was performed in relevant reviews identified by the searches. Full search strategies can be seen in appendices S1-S2 .
STUDY SELECTION AND DATA EXTRACTION
Abstract screening was undertaken, followed by full-text assessment by JC and Y-SC. Papers which met eligibility criteria were included. If a paper did not explicitly state these criteria, authors were contacted via email.
A data extraction form was created for quantitative and qualitative studies. From quantitative studies, the data extracted included incidence of postnatal PTSD for women who underwent different modes of birth in the form of Odds Ratios comparing the mode of birth studied with SVD where possible. For the qualitative studies, key findings (i.e. themes) were extracted.
QUALITY APPRAISAL
Quality was assessed by JC and Y-SC using the Newcastle-Ottawa Scale (NOS) for quantitative cohort studies, the Centre for Evidence Based Medicine (CEBM) Critical Appraisal Checklist for cross-sectional studies and the Critical Appraisal Skills Programme (CASP) tool for qualitative studies.
OUTCOME MEASURES