Additional LOS related to patient safety events for each PSI
| PSI | LOS |
| PSI 18—obstetric trauma during vaginal delivery with instrument | 0.4688* 95% CI (0.4008 to 0.5368) |
| PSI 19—obstetric trauma during vaginal delivery without instrument | 0.5126* 95% CI (0.4822 to 0.5427) |
| PSI 20—obstetric trauma during caesarean delivery | 1.0874* 95% CI (0.9027 to 1.272) |
↵*p<0.001
LOS, length of stay; PSI, Patient Safety Indicators.