Table 2

Proportions and associations of mode of birth outcomes, pain relief treatment and short-term maternal outcomes with induction of labour for non-medical reasons, New South Wales, Australia 2001–2016 (N=474 652)

474 652210 779263 873
Total birthsPrimiparous birthsMultiparous births
Proportion
N (%)
AOR (99% CI)*Proportion
n (%)
AOR (99% CI)†Proportion
n (%)
AOR (99% CI)†
Mode of birth outcomes
Vaginal birth
 Spontaneous onset of labour312 801 (77.2)NA‡112 783 (62.3)NA‡200 018 (89.2)NA‡
 Induction of labour47 315 (68.2)NA‡12 657 (42.7)NA‡34 658 (87.2)NA‡
Instrumental vaginal birth
 Spontaneous onset of labour53 512 (13.2)Ref.43 303 (23.9)Ref.10 209 (4.6)Ref.
 Induction of labour11 311 (16.3) 1.51(1.46 to 1.56) 9296 (28.0) 1.66 (1.59 to 1.73) 3015 (7.6) 1.61 (1.52 to 1.70)
Caesarean section
 Spontaneous onset of labour38 942 (9.6)Ref.25 059 (13.8)Ref.13 883 (6.2)Ref.
 Induction of labour10 771 (15.5) 1.92 (1.86 to 1.98) 8681 (29.3) 3.02 (2.90 to 3.15) 2090 (5.3) 0.78 (0.73 to 0.83)
Pain relief treatment§
No pain relief treatment
 Spontaneous onset of labour63 901 (15.8)NA§11 245 (6.2)NA§52 656 (23.5)NA§
 Induction of labour4694 (6.8)NA§507 (1.7)NA§4187 (10.5)NA§
Pharmacological medication¶
 Spontaneous onset of labour224 109 (55.3)Ref.94 548 (52.2)Ref.129 561 (57.8)Ref.
 Induction of labour27 256 (39.3) 1.85 (1.78 to 1.94) 8078 (27.3) 1.95 (1.72 to 2.20) 19 178 (48.2) 1.88 (1.80 to 1.97)
Epidural/spinal analgesia
 Spontaneous onset of labour115 427 (28.5)Ref.74 896 (41.3)Ref.40 531 (18.1)Ref.
 Induction of labour37 331 (53.8) 5.19 (4.97 to 5.42) 21 026 (71.0) 6.24 (5.53 to 7.03) 16 305 (41.0) 4.58 (4.36 to 4.81)
Maternal outcomes
Episiotomy**
 Spontaneous onset of labour63 749 (17.4)Ref.47 571 (30.5)Ref.16 178 (7.7)Ref.
 Induction of labour13 135 (22.4) 1.62 (1.57 to 1.67) 8641 (41.2) 1.61 (1.55 to 1.67) 4494 (11.9) 1.59 (1.51 to 1.66)
3rd/4th degree tear**
 Spontaneous onset of labour10 173 (2.8)Ref.7629 (4.9)Ref.2544 (1.2)Ref.
 Induction of labour1156 (2.0) 0.82 (0.75 to 0.89) 879 (4.2) 0.89 (0.81 to 0.98) 277 (0.7) 0.65 (0.55 to 0.76)
Vaginal repair**
 Spontaneous onset of labour240 404 (65.6)Ref.131 514 (84.3)Ref.108 890 (51.8)Ref.
 Induction of labour40 369 (68.9) 1.31 (1.28 to 1.35) 18 710 (89.3) 1.57 (1.47 to 1.67) 21 659 (57.5) 1.23 (1.20 to 1.27)
Postpartum haemorrhage
 Spontaneous onset of labour5111 (1.3)Ref.2774 (1.5)Ref.2337 (1.0)Ref.
 Induction of labour1287 (1.9) 1.68 (1.55 to 1.82) 700 (2.4) 1.63 (1.46 to 1.82) 587 (1.5) 1.75 (1.54 to 1.98)
  • Associations in bold are statistically significant p≤0.01.

  • *Multinominal and multivariate logistic regression models were adjusted for maternal age, country of birth, socioeconomic status, gestational age, parity.

  • †Multinominal and multivariate logistic regression models were adjusted for maternal age, country of birth, socioeconomic status, gestational age.

  • ‡In the multinominal regression model vaginal birth is the reference group.

  • §In the multinomial regression model no pain relief treatment is the reference group.

  • ¶Pharmacological pain medication (ie, nitrous oxide, systematic opioid, local administered to perineum, pudendal, morphine and pethidine—other than epidural analgesia).

  • **The maternal outcomes episiotomy, 3rd/4th tear, vaginal repair are calculated for vaginal births for the total population (n=424 939), first births (n=177 039) and second-8 births (n=247 900).

  • aOR, adjusted OR; NA, not applicable.