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.