Fig. 1

Flow chart of patients who met inclusion/exclusion criteria for the study population. *Robson group 1 comprising nullipara, singleton cephalic ≥37 weeks in spontaneous labour, ** Robson group 2 comprising nullipara, singleton cephalic ≥37 weeks who were induced or underwent caesarean before labour, *** Robson group 2a comprising nullipara, singleton cephalic ≥37 weeks who had labour induced. **** Robson group 2b; comprising nullipara, singleton cephalic ≥37 weeks who underwent caesarean section before labour