Table 2 Univariate analysis of antepartum characteristics of nulliparous in train cohort

Maternal age (y)

28.2 ± 3.1

29.4 ± 3.4

<0.001

Weight (kg)

70.7 ± 9.1

73.1 ± 10.4

<0.001

Height (cm)

162.1 ± 4.5

160.5 ± 4.4

<0.001

Uterine height (cm)

35.4 ± 2.2

36.2 ± 2.4

<0.001

Abdominal circumference (cm)

100.9 ± 6.1

103.6 ± 6.8

<0.001

Gestational age (wk)

39 (39-40)

40 (39-41)

0.003

Estimated fetal weight (g)

3500 (3200-3600)

3500 (3300-3700)

<0.001

Initial cervical dilation (cm)

0.025

 0 (0 points)

2491 (97.4)

389 (99.2)

 1-2 (1 points)

67 (2.6)

3 (0.8)

Initial station

<0.001

 -3 (0 points)

783 (30.6)

179 (45.7)

 -2 (1 points)

1723 (67.4)

209 (53.3)

 -1 or 0 (2 points)

52 (2.0)

4 (1.0)

 + 1 (3 points)

Initial cervical effacement (%)

<0.001

 0-30 (0 points)

2 (0.1)

3 (0.8)

 40-50 (1 points)

430 (16.8)

90 (23.0)

 60-70 (2 points)

1918 (75.0)

287 (73.2)

 ≥ 80 (3 points)

208 (8.1)

12 (3.1)

Initial cervical position

0.336

 Posterior (0 points)

893 (34.9)

122 (31.1)

 Mid position (1 points)

1613 (63.1)

262 (66.8)

 Anterior (2 points)

52 (2.0)

8 (2.0)

Initial cervical consistency

<0.001

 Firm (0 points)

35 (1.4)

9 (2.3)

 Medium (1 points)

1256 (49.1)

239 (61.0)

 Soft (2 points)

1266 (49.5)

144 (36.7)

Bishop Score

<0.001

 <6

1853 (72.4)

332 (84.7)

 ≥ 6

705 (27.6)

60 (15.3)