Table 3.

Emergency CSs in a low-risk subgroup (nulliparous women who gave birth to a child in cephalic presentation at ≥37 weeks+0 days in spontaneous labour)

Singleton deliveries, subgroup	Subgroup, all	Emergency CS
	n (% of all)	n (% within category)	OR	95% CI
	74 002 (100)	8698 (11.8)
Year
2009	19 353 (26)	2357 (12.2)	Ref
2010	19 186 (26)	2338 (12.2)	0.95	0.89 to 1.02
2011	17 884 (24)	1994 (11.2)	0.87	0.81 to 0.93
2012	17 579 (24)	2009 (11.4)	0.94	0.88 to 1.01
Size of maternity unit
Small	4343 (6)	543 (12.5)	1.02	0.92 to 1.13
Medium	27 970 (38)	3416 (12.2)	Ref
Large	41 689 (56)	4739 (11.4)	0.82	0.77 to 0.86
Weekend delivery (yes)	22 516 (30)	2672 (11.9)	1.02	0.97 to 1.08
Night delivery 20:00–07:59 (yes)	35 380 (48)	4239 (12.0)	1.05	1.00 to 1.10
Maternal age (years)
15–19	2282 (3)	158 (6.9)	0.65	0.55 to 0.78
20–34	64 080 (87)	7106 (11.1)	Ref
35–44	7640 (10)	1434 (18.8)	1.76	1.64 to 1.89
Maternal smoking (yes)	9708 (13)	1143 (11.8)	1.04	0.97 to 1.12
Maternal BMI
14.0–18.4	3644 (5)	275 (7.6)	0.75	0.66 to 0.86
18.5–24.9	50 370 (68)	5245 (10.4)	Ref
25.0–29.9	13 432 (18)	1959 (14.6)	1.40	1.32 to 1.49
30–34.9	4572 (6)	789 (17.3)	1.76	1.61 to 1.92
35.0+	1984 (3)	430 (21.7)	2.18	1.93 to 2.46
Maternal height ≤163 cm (yes)	17 698 (24)	3008 (17.0)	1.78	1.69 to 1.88
Complication (yes)	7880 (11)	1572 (19.9)	1.98	1.85 to 2.11
Augmentation of labour (yes)	32 219 (44)	5411 (16.8)	1.57	1.49 to 1.66
Term
37+0–41+6	71 322 (96)	8089 (11.3)	Ref
≥42+0	2680 (4)	609 (22.7)	1.96	1.77 to 2.18
Female baby (yes)	36 265 (49)	3877 (10.7)	0.87	0.83 to 0.91
Fetal distress (yes)	22 086 (30)	4311 (19.5)	2.38	2.26 to 2.51
Cephalopelvic disproportion (yes)	2093 (3)	1293 (61.8)	13.12	11.89 to 14.48
Macrosomia (yes)	1139 (2)	381 (33.4)	3.36	2.92 to 3.87

Distribution of subgroup births and proportion of emergency CS according to risk factors. OR with 95% CI based on a multivariable logistic regression model.

BMI, body mass index; CS, caesarean section; n, number; Ref, reference group.