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).