Table 1 Characteristics prior to study entry

Maternal age (years) - mean {SD}

 Under 20

 20–24

 25–29

 30–34

 35–39

 40+

28.9

24

93

133

177

66

10

{5.6}

(4.8)

(18.5)

(26.4)

(35.2)

(13.1)

(2.0)

29.3

24

79

148

180

71

13

{5.5}

(4.7)

(15.3)

(28.7)

(35.0)

(13.8)

(2.5)

Gestational age at entry (weeks) - mean {SD}

 37⁺⁰ – 39⁺⁶

 40⁺⁰ – 41⁺⁶

 42⁺⁰ or above

40.4

150

320

32

{1.2}

(29.9)

(63.8)

(6.4)

40.3

167

315

32

{1.2}

(32.5)

(61.3)

(6.2)

Index of Multiple Deprivation – quintile

 1^st (Least deprived)

 2^nd

 3^rd

 4^th

 5^th (Most deprived)

 Wales – not derived

 Postcode missing

64

72

83

112

95

66

11

(15.0)

(16.9)

(19.5)

(26.3)

(22.3)

72

63

91

129

88

59

13

(16.3)

(14.2)

(20.5)

(29.1)

(19.9)

Ethnic group:

 White

 Indian

 Pakistani

 Bangladeshi

 Black African

 Black Caribbean

 Any other ethnic group

 Not known/missing

415

20

9

2

14

7

29

7

(83.7)

(4.0)

(1.8)

(0.4)

(2.8)

(1.4)

(5.9)

434

14

7

1

10

2

42

5

(85.1)

(2.8)

(1.4)

(0.2)

(2.0)

(0.4)

(8.2)

BMI (at booking visit)

 - mean {SD}

 Height and/or weight not known

25.2

18

{5.2}

25.2

11

{5.3}

Onset of labour:

 Spontaneous

 Induced

309

193

(61.6)

(38.5)

293

222

(56.9)

(43.1)

Diagnosis of pre-eclampsia

12

(2.4)

22

(4.3)

Diagnosis of delay requiring intervention

266

(53.1)

272

(52.8)

Systemic opioids given prior to epidural

 Pethidine

 Diamorphine

 Remifentanil

 Morphine

 Meptid

142

103

38

0

0

3

(28.3)

(72.5)

(26.8)

(0.0)

(0.0)

(2.1)

137

97

38

1

0

3

(26.6)

(70.8)

(27.7)

(0.7)

(0.0)

(2.2)

Epidural technique:

 Epidural

 Combined spinal epidural

485

17

(96.6)

(3.4)

496

18

(96.5)

(3.5)

Woman’s pain score for last contraction - median [IQR]

Missing

10

59

[0 to 32]

10

55

[0 to 30]

Able to perform straight leg raise

Missing

381

29

(80.4)

408

22

(82.8)

Spontaneous vaginal birth

197

(39.2)

181

(35.2)