A. Model structure
A decision model was developed in the form of a decision tree to compare the short-term outcomes for women who received PG as an inpatient with those who received a balloon catheter as an outpatient. A health services perspective was chosen for the evaluation, from hospital admission until discharge home of mother and baby. Women moved through mutually exclusive model pathways, according to transition probabilities associated with each model arm. The model distinguished the two comparators (balloon group, PG group) for nulliparous vs parous women and their probabilities of mode of birth (unassisted vaginal, instrumental or caesarean section (CS)) and baby requiring nursery admission vs postnatal ward care. The model structure is illustrated in the Supplementary material (Figures S1 & S2).