Data Extraction and Quality Assessment
Data extraction for included studies was performed independently by at least two authors (AAB, KAB, MS and DG) using REDCap electronic data capture tools hosted at Massachusetts General Hospital, Boston USA.11 Data on the location, study year, clinical setting, study design, study population, planned and actual mode of delivery, and any reported maternal and neonatal outcomes were extracted. A third reviewer resolved disagreements between reviewers until consensus was reached.
Quality assessment of studies was performed using the methodological index for non-randomized studies (MINORS) (Table S2)12. This tool was developed for quality assessment in surgical research, where it is anticipated that most studies will be observational or non-randomized. Studies are rated on 12 items and assess clarity in the aims, inclusion criteria, and endpoints of the study, as well as the extent to which studies had a prospective design, comparison group, reported and described definitions, length of follow-up of outcomes, and included appropriate statistical analysis. Studies received ratings of “Not Reported” (0 points), “Reported but inadequate” (1 point), and “Reported and adequate” (2 points). A score of 16 or greater represents a high-quality study. At least two authors (AAB, KAB, MS and DG) independently rated studies and where a disagreement occurred, consensus was reached through discussion with a third independent author. Studies were not excluded based on quality assessment, but sensitivity analyses were performed using studies with a score ≥16, indicating a high-quality study.