Study selection
The inclusion and exclusion criteria of the study are as in Table 1. Only prospective studies reporting clinical outcomes of planned CS versus planned vaginal birth at term for singleton pregnancy were included. All cases where vaginal birth was the intended birth route regardless of whether this resulted in emergency caesarean section, forceps delivery, ventouse delivery or spontaneous vaginal birth were included. Studies that classified women with planned VD who eventually had planned VD, and women with planned VD who eventually had emergency CS as separate interventions were included. This is because these studies added value to our overall objective of collecting core outcome and outcome measurements, and our review did not assess results of outcomes between the two different groups of planned VD including emergency birth versus planned CS, where incomplete groups would lead be a major weakness.
Outcomes reported for multiple pregnancy, preterm birth and vaginal birth after CS (VBAC), also known as trial of labour after CS (TOLAC), were not included as these topics would warrant separate core outcome sets 14, 15. Studies investigating placenta praevia, HIV infection, contracted pelvis were excluded as these were clear indications for CS. Abstracts, reviews and conference proceedings were excluded. Retrospective studies were excluded due to high risk of reporting bias. Studies comparing planned mode of birth of second pregnancy versus first pregnancy were excluded as they were not explicitly comparing planned CS versus planned VD. There were no language restrictions.