Table 1 Characteristics of the women, use of pain relief, labour outcomes and infant data

 Age (years), mean (SD)

26.5 (4.8)

27.6 (4.6)

28.3 (5.0)

 Born in Sweden (%)

91.3

89.7

90.2

 Higher education (%)

35

44.8

54.2

 Single parent (%)

14.5

18.4

15.7

 Smoking 3 months prior to pregnancy (%)

23.0

19.5

19.7

 Body mass index in early pregnancy, mean (SD)

24.4 (5.0)

24.2 (3.8)

24.9 (4.1)

 Cervix dilatation at admission (cm), mean (SD)

3.6 (1.5)

4 (1.6)

3.6 (1.8)

 Membranes ruptured before admission (%)

30.5

28.7

33.3

MA vs. SC

EA vs. SC

MA vs. EA

OR (CI)^a

OR (CI)^a

OR (CI)^b

 Nitrous Oxide (%)

95.1

95.4

93.8

1.89 (0.43–8.37)

1.52 (0.39–5.96)

0.80 (0.17–3.75)

 Sterile water injections (%)

12.2

4.7

10.0

1.15 (0.42–3.14)

0.40 (0.11–1.40)

0.35 (0.10–1.17)

 TENS (%)

14.5

12.6

48.1

0.17 (0.77–0.37)

0.16 (0.73–0.34)

0.94 (0.38–2.33)

 Morphine (%)

10.8

1.2

6.3

1.87 (0.59–5.95)

0.17 (0.20–1.53)

0.09 (0.01–0.76)

 Epidural analgesia (%)

61.4

46.0

69.9

0.62 (0.32–1.20)

0.35 (0.19–0.67)

0.57 (0.31–1.06)

 Mode of Delivery

 Normal vaginal (%)

74.7

74.7

74.7

0.97 (0.46–2.02)

0.94 (0.46–1.91)

0.97 (0.48–1.99)

 Instrumental vaginal (%)

16.9

19.5

12.0

1.52 (0.61–3.81)

1.93 (0.81–4.63)

1.27 (0.56–2.87)

 Caesarean (%)

8.4

5.7

13.3

0.64 (0.23–1.79)

0.41 (0.14–1.26)

0.65 (0.20–2.14)

HR (CI 95 %)^a

HR (CI 95 %)^a

HR (CI 95 %)^b

 Duration of labour (minutes) mean (SD) c

619 (378)

500 (319)

615 (398)

1.03 (0.75–1.41)

1.44 (1.06–1.97)

1.41 (1.03–1.91)

Infant data

OR (CI)^a

OR (CI)^a

OR (CI)^b

 Transferal to neonatal care unit (%)

3.6

11.5

4.9

0.91 (0.19–4.31)

2.82 (0.82–9.68)

3.11 (0.81–11.98)

p

p

p

 Apgar score <7 at 5 minutes (%)

1.2

2.3

0

1.00

0.68

0.69

 Umbilical cord arterial pH, mean (SD)

7.3 (0.7)

7.2 (0.7)

7.3 (0.8)

1.00

0.52

0.45

 Umbilical cord venous pH, mean (SD)

7.3 (0.7)

7.3 (0.8)

7.3 (0.6)

1.00

0.68

0.69

 Head circumference (cm), mean (SD)

34.9 (1.4)

34.9 (1.3)

35 (1.3)

 Birth weight (grams), mean (SD)

3508 (410)

3590 (456)

3654 (493)