Inclusion of papers
RCTs, pilot and feasibility studies (with or without a comparator group) were included. Retrospective studies (e.g. case-control or cohort studies) were excluded because CONSORT-NPT guidance focuses on reporting standards in RCTs. Simulation and animal studies were included if they otherwise met the inclusion criteria. There were no language restrictions. AVB devices were not limited to a single type or manufacturer. Any type of comparator was included (i.e. spontaneous vaginal birth (SVB), Caesarean section or another AVB device).
After removal of duplicate records, titles and abstracts of citations were screened for eligibility by two researchers (EJH and SR) using predetermined selection criteria. Reference lists of retrieved articles were manually searched for additional references, including published protocols for included studies. Each abstract was independently read by at least two authors and full-text articles meeting the inclusion criteria analysed by at least two authors (EJH, SR or NSB). Discrepancies were resolved by discussion with NSB.