Table 2

Labour and birth-related factors

Cases n=1041Controls n=1984Unadjusted analysis
n%n%OR(95% CI)P value
Maternal complications identified at start of labour care*0.30
 None101297.8194398.31
 One or more232.2341.71.30(0.79 to 2.13)
 Missing67
Fetal complications identified at start of labour care†<0.0001
 None96092.8190896.5
 One or more757.2693.52.16(1.52 to 3.06)
 Missing67
Stage of labour at admission0.03
 Latent24323.543021.71.07(0.90 to 1.26)
 Active first stage70968.5134067.61
 Passive second stage272.6804.00.64(0.43 to 0.94)
 Active second stage565.41316.60.81(0.57 to 1.14)
 Missing63
Duration of first stage of labour‡0.21
 Within guidance88184.6170686.01
 Possibly prolonged201.9211.11.84(0.92 to 3.68)
 Not recorded14013.525712.91.05(0.85 to 1.31)
Duration of second stage of labour§0.02
 Within guidance88284.7175288.31
 Possibly prolonged706.7924.61.51(1.06 to 2.15)
 Not recorded898.61407.11.26(0.97 to 1.65)
Immersion in water during labour0.002
 No53952.1115258.21
 Yes49647.982941.81.28(1.10 to 1.49)
 Missing33
Pethidine/Diamorphine during labour0.002
 No88785.7177989.81
 Yes14814.320310.21.46(1.16 to 1.85)
 Missing62
Duration between pethidine/diamorphine and birth (hours)¶0.29
 Mean (SD)3.8(2.4)3.5(2.6)1.05(0.96 to 1.15)
 Median (IQR)3.3(2.0 to 5.4)2.9(1.5 to 4.7)
 Missing (n)2239
Fetal heart rate concerns identified<0.0001
 No96293.0194298.01
 Yes737.0392.03.78(2.62 to 5.45)
 Missing63
Maternal complications identified during labour (before birth)**0.78
 None101998.5194898.31
 One or more161.6331.70.93(0.54 to 1.59)
 Missing63
Fetal complications identified during labour (before birth)††<0.0001
 None79877.1186093.91
 One or more23722.91216.14.57(3.61 to 5.77)
 Missing63
Obstetrician consulted for maternal compromise during labour0.58
 No102198.7195998.81
 Yes141.3231.21.17(0.67 to 2.03)
 Missing62
Obstetrician consulted for fetal compromise during labour<0.0001
 No96893.5192597.11
 Yes676.5572.92.34(1.63 to 3.35)
 Missing62
Shoulder dystocia<0.0001
 No97293.9195898.81
 Yes636.1241.25.29(3.27 to 8.55)
 Missing62
Birth weight (g)<0.0001
 <2500252.4120.64.65(2.34 to 9.24)
 2500–299913012.623311.71.25(0.95 to 1.63)
 3000–349938337.085543.21
 3500–399933031.967233.91.10(0.90 to 1.33)
 4000–449913713.21839.21.67(1.29 to 2.16)
 ≥4500313.0261.32.66(1.57 to 4.52)
 Missing53
Birth in water0.01
 No78976.2142571.91
 Yes24623.855728.10.80(0.67 to 0.95)
 Missing62
Mode of birth0.03
 Spontaneous vertex101498.0196299.01
 Vaginal breech‡‡80.810.115.48(1.87 to 128.32)
 Instrumental131.3180.91.40(0.62 to 3.13)
 Missing63
  • *Maternal tachycardia; hypertension; proteinuria; maternal fever; vaginal blood loss; prolonged membrane rupture; pain differing from contractions.

  • †Significant meconium; non-significant meconium; abnormal presentation; high/free floating head; suspected fetal growth restriction/macrosomia; suspected anhydramnios/polyhydramnios; fetal heart rate abnormality; fetal heart rate decelerations; reduced fetal movements in last 24 hours.

  • ‡From start of active first stage to start of active second stage: within guidance ≤12 hours (nulliparous and multiparous); possibly prolonged >12 hours (nulliparous and multiparous).

  • §From start of active second stage to birth: within guidance ≤2 hours (nulliparous), ≤1 hour (multiparous); possibly prolonged >2 hours (nulliparous), >1 hour (multiparous).

  • ¶In those who received pethidine/diamorphine.

  • **Maternal tachycardia; hypertension; maternal fever; vaginal blood loss; prolonged membrane rupture; pain differing from contractions.

  • ††Significant meconium; confirmed/suspected first stage delay; confirmed/suspected second stage delay; obstetric emergency; abnormal presentation; transverse/oblique lie; high/free floating head; fetal heart rate abnormality; fetal heart rate decelerations.

  • ‡‡All vaginal breech births were undiagnosed before admission. One woman had a precipitate birth, shortly after admission. In the remaining eight, abnormal presentation was noted on admission or during labour and five women were seen by an obstetrician in the AMU.

  • AMU, alongside midwifery unit.