Table 1 Maternal characteristics and obstetric outcomes according to labour duration status after stratification by parity.

Labour duration

 < 10 h

 ≥ 10 h

 < 5 h

 ≥ 5 h

Variable

N = 6597

N = 5844

N = 13,342

N = 11,899

Maternal age (years), mean (SD)

29.1 (5.0)

29.1 (4.8)

32.0 (4.6)

31.7 (4.6)

Pre-pregnancy BMI (kg/m²), median (IQR)

20.0 (18.8–21.7)

20.2 (18.9–21.9)

20.4 (19.1–22.2)

20.6 (19.1–22.6)

GWG (kg), mean (SD)

10.5 (3.8)

10.9 (4.1)

10.0 (3.7)

10.4 (7.3)

Maternal smoking during pregnancy, % (n)

3.3 (216)

3.9 (225)

4.8 (642)

5.1 (608)

Maternal alcohol consumption, % (n)

1.3 (89)

1.1 (67)

3.9 (520)

3.7 (440)

Maternal educational status, % (n)

 < 10 years

3.8 (248)

3.4 (201)

4.8 (647)

5.2 (615)

10–12 years

29.2 (1925)

29.3 (1714)

31.3 (4176)

33.0 (3931)

13–16 years

65.6 (4329)

65.5 (3830)

62.4 (8331)

60.6 (7208)

 ≥ 17 years

1.4 (95)

1.7 (99)

1.4 (188)

1.2 (145)

Annual household income, % (n)

 < 2,000,000 JPY

5.9 (388)

6.0 (353)

5.2 (699)

5.6 (672)

2,000,000–5,999,999 JPY

66.8 (4406)

66.4 (3881)

68.6 (9154)

69.9 (8322)

6,000,000–9,999,999 JPY

23.4 (1543)

23.1 (1351)

22.0 (2940)

20.5 (2443)

 ≥ 10,000,000 JPY

3.9 (260)

4.4 (259)

4.1 (549)

3.9 (462)

Neonatal birth weight (g), mean (SD)

2965 (333)

3041 (328)

3087 (351)

3129 (353)

Hypertensive disorders of pregnancy, % (n)

2.1 (139)

1.7 (102)

1.0 (133)

1.0 (121)

Apgar scores < 7 at 1 min after birth, % (n)

1.0 (65)

1.1 (67)

0.7 (95)

0.9 (102)

Apgar scores < 7 at 5 min after birth, % (n)

0.3 (19)

0.4 (25)

0.2 (28)

0.2 (27)

UmA-pH < 7.2, % (n)

6.4 (422)

8.9 (520)

4.1 (545)

4.8 (570)

UmA-pH < 7.1, % (n)

1.0 (66)

1.5 (85)

0.6 (81)

0.8 (92)