When infiltration was added as a method for pain relief,
18% were still delivered without pain relief. Multiparas were more likely than
primiparas to be delivered without potent pain relief, odds ratio (OR) 2.29 95%
confidence interval (CI) (2.20–2.38). Compared with women delivered by
vacuum extraction due to prolonged labor, those with signs of fetal distress
were more likely to be delivered without potent pain relief