Table 1 Estimated mean probability ratios and 95% credible intervals of spontaneous labour, no anaesthesia, unassisted vaginal birth and no episiotomy
| Â | Probability Ratios | |||||||
|---|---|---|---|---|---|---|---|---|
Spontaneous Labour | No Anaesthesia | Unassisted VB | No Episiotomy | |||||
(N = 4611) | (N = 2223) | (N = 1636) | (N = 1322) | |||||
M | 95% CI | M | 95% CI | M | 95% CI | M | 95% CI | |
MATERNAL SOCIO-DEMOGRAPHIC CHARACTERISTICS | ||||||||
 Maternal age (+  5 years)a | 0.94 | 0.91–0.98 | 0.90 | 0.82–0.98 | 0.99 | 0.97–1.00 | 0.96 | 0.87–1.00 |
 Completed secondary education | 1.21 | 1.06–1.38 | 1.21 | 0.87–1.69 | 0.98 | 0.94–1.02 | 0.94 | 0.75–1.15 |
 Identifies as Aboriginal/Torres Strait Islander | 1.01 | 0.70–1.33 | 0.94 | 0.56–2.31 | 0.91 | 0.69–1.00 | 0.80 | 0.27–1.08 |
Area of residence | ||||||||
 Major city | 1.00 |  | 1.00 |  | 1.00 |  | 1.00 |  |
 Inner regional | 1.05 | 0.96–1.14 | 1.31 | 1.05–1.69 | 1.00 | 0.98–1.02 | 1.02 | 0.94–1.15 |
 Outer regional | 1.06 | 0.97–1.16 | 1.75 | 1.33–2.44 | 1.00 | 0.97–1.02 | 1.05 | 0.98–1.22 |
 Remote/very remote | 0.94 | 0.74–1.16 | 1.59 | 0.91–3.86 | 1.03 | 1.00–1.08 | 1.01 | 0.77–1.23 |
PREGNANCY DETAILS/COMPLICATIONS | ||||||||
Parity | ||||||||
 Multiparous – no previous CS | 1.00 |  | 1.00 |  | 1.00 |  | 1.00 |  |
 Multiparous – previous CS | 0.38 | 0.32–0.45 | 0.64 | 0.50–0.82 | 0.55 | 0.28–0.81 | 0.72 | 0.32–0.98 |
 Primiparous | 0.81 | 0.74–0.88 | 0.53 | 0.41–0.68 | 0.79 | 0.59–0.93 | 0.66 | 0.32–0.93 |
Multiple birth | 0.47 | 0.28–0.70 | 0.50 | 0.32–0.87 | 0.06 | 0.00–0.56 | – |  |
Pre-pregnancy BMI (+ 5 kg/m2)b | 0.96 | 0.93–0.98 | 1.00 | 0.96–1.05 | 1.00 | 1.00–1.01 | 1.02 | 1.00–1.09 |
Gestational age (+  1 week)c | 0.95 | 0.92–0.97 | 0.95 | 0.91–0.99 | 1.00 | 0.99–1.00 | 0.97 | 0.91–1.00 |
Gestational diabetes | 0.70 | 0.59–0.82 | 0.94 | 0.70–1.35 | 0.97 | 0.90–1.01 | 1.03 | 0.87–1.25 |
High blood pressure | 0.51 | 0.42–0.60 | 0.73 | 0.57–0.96 | 1.02 | 0.99–1.06 | 0.95 | 0.72–1.07 |
Low lying placenta | 0.88 | 0.76–1.00 | 0.80 | 0.62–1.05 | 0.98 | 0.92–1.01 | 1.02 | 0.87–1.19 |
Other risk factors | 0.76 | 0.69–0.82 | 1.15 | 0.97–1.40 | 1.00 | 0.97–1.01 | 1.00 | 0.91–1.08 |
ANTENATAL AND INTRAPARTUM CARE | ||||||||
Model of care | ||||||||
 Private obstetric care | 1.00 |  | 1.00 |  | 1.00 |  | 1.00 |  |
 Standard public care | 1.40 | 1.29–1.54 | 1.35 | 1.07–1.77 | 1.00 | 0.97–1.02 | 1.09 | 1.01–1.83 |
 GP shared care | 1.48 | 1.35–1.62 | 1.67 | 1.32–2.24 | 1.02 | 1.00–1.05 | 1.08 | 1.00–1.32 |
 Public midwifery continuity care | 1.66 | 1.50–1.86 | 1.57 | 1.20–2.18 | 1.02 | 1.00–1.07 | 1.07 | 1.00–1.31 |
 Private midwifery care | 1.93 | 1.64–2.25 | 3.35 | 0.96–109.68 | 1.03 | 0.98–1.09 | 1.14 | 1.01–1.58 |
Known care providers – labour/birth | ||||||||
 None of them | 1.00 |  | 1.00 |  | 1.00 |  | 1.00 |  |
 Some of them | – |  | 0.76 | 0.63–0.91 | 0.95 | 0.87–0.98 | 0.96 | 0.83–1.03 |
 All of them | – |  | 1.36 | 0.84–2.76 | 1.01 | 0.97–1.06 | 1.07 | 0.95–1.34 |
Continuity of care during labour/birth | – |  | 1.45 | 1.21–1.78 | 1.02 | 1.00–1.05 | 1.03 | 0.98–1.16 |
Felt rushed/hurried during labour | – |  | 1.19 | 0.92–1.60 | 0.94 | 0.84–0.99 | 1.09 | 1.00–1.38 |
LABOUR/BIRTH EXPERIENCE | ||||||||
Augmentation of labour | ||||||||
 Yes | 1.00 |  | 1.00 |  | 1.00 |  | 1.00 |  |
 No | – |  | 2.72 | 2.15–3.56 | 1.01 | 0.99–1.03 | 1.05 | 1.00–1.19 |
 Not sure | – |  | 1.31 | 0.85–2.36 | 0.93 | 0.78–1.00 | 0.91 | 0.52–1.12 |
Had continuous fetal monitoring | – |  | 0.47 | 0.35–0.63 | 0.92 | 0.82–0.98 | 0.95 | 0.80–1.02 |
Freedom of movement throughout labour | – |  | 1.54 | 1.20–2.01 | 1.02 | 1.00–1.06 | 1.08 | 0.99–1.35 |
Water immersion during labour | – |  | 1.05 | 0.85–1.36 | 1.00 | 0.98–1.02 | 1.03 | 0.96–1.16 |
Birth outside business hours | – |  | – |  | 1.01 | 0.99–1.03 | 1.01 | 0.93–1.10 |
Non-supine position during birth | – |  | – |  | – |  | 1.11 | 1.01–1.41 |