Women’s characteristics
A total of 13,670 women delivered in the hospital during the study period. Of these, 2359 (17.4%) matched our inclusion criteria of low risk singleton pregnancy from 40+0 to 41+6 GW with the foetus in cephalic presentation (Figure 1 ). Among the included women SOL was observed in 1585 women (67.2%), while among 774 cases of IOL, 456 (58.9%) were induced from 40+0 to 40+6 GW, and 318 (41.1%) from 41+0 to 41+6 GW.
Some imbalances among groups were observed (Table 1 ). Women undergoing IOL at 40 GW had a significantly higher level of education compared to the SOL group (20.0% vs 13.3%, p=0.001). Significantly more women were unmarried and overweight in the IOL at 41 GW group compared to SOL, and more women were overweight comparing IOL at 41 and 40 weeks (unmarried women: 2.2% vs 0.9%, p=0.040; overweight women: 29.9% vs 23.2% in IOL at 40 GW vs 23.0 in SOL, p=0.031). IOL group at 41 GW had an increased frequency of newborns with a birth weight between 3500 and 4000 grams (19.2% vs 12.5% in IOL at 40 GW vs 14.8% in SOL, p=0.035) and above 4000 grams (2.5% vs 2.4% in IOL at 40 GW vs 0.8% in SOL, p=0.006). Women with SOL were most often multiparous (52.4% vs 43.0% in IOL at 40 GW vs 37.7% in IOL at 41 GW, p<0.001) and more frequently assisted at delivery by nurses (56.7% vs 44.9% vs 36.5%, p<0.001), while mid-level medical staff (either senior house officers or registrars) was more often involved in IOL groups (30.7% vs 30.2% vs 14.1%, p<0.001).