factors PR(%) Waldχ2 P OR 95% CI 95% CI
lower range Upper range
delivery times 17.104 <0.001 2.046 1.457 2.873
cesarean section times 30.252 <0.001
0-1 87.3 1.000
≥2 12.7 4.985 2.812 8.837
Interval between previous cesarean section and current deliver (years) 5.351 0.021 0.951 0.911 0.992
placental implantation under ulreasound 55.655 <0.001
no 63.7 1.000
yes 18.9 3.788 2.474 5.800
suspecious 17.4 3.143 2.056 4.805
placental implantation under MRI 57.059 <0.001
no 16.7 1.000
yes 5.6 11.892 4.846 29.185
suspecious 13.5 7.230 3.996 13.083
do not perform MRI 64.1 3.047 1.993 4.657
placental implantation during operation 142.683 <0.001
no 1.000
yes 9.858 6.713 14.478
suspecious 2.241 1.466 3.426
Type of placenta previa 26.573 <0.001
marginal 25.7 1.000
partial 5.1 1.044 .516 2.115
complete 69.1 2.327 1.657 3.268