Table 2.

Cox regression results for risk factors for undergoing surgical treatment for UI

Risk factor	No operation (N=32 501)	UI operation (N=762)	Unadjusted		Adjusted
	N (%)	N (%)	HR (95% CI)	p Value	HR (95% CI)	p Value
Mode of delivery
SVD/breech only	19 776 (60.8%)	533 (69.9%)	1.00		1.00
CS only	2524 (7.8%)	18 (2.4%)	0.40 (0.25 to 0.64)	<0.001	0.51 (0.32 to 0.83)	0.007
Instrumental (at least one forceps)	8433 (25.9%)	172 (22.6%)	0.86 (0.72 to 1.02)	0.08	0.86 (0.72 to 1.03)	0.10
Instrumental (at least one, but no forceps)	639 (2.0%)	12 (1.6%)	1.72 (0.97 to 3.05)	0.06	1.65 (0.93 to 2.94)	0.09
SVD+CS	1129 (3.5%)	27 (3.5%)	1.12 (0.76 to 1.65)	0.57	1.07 (0.73 to 1.58)	0.72
Age at first delivery
Under 20 years	5510 (17.0%)	182 (23.9%)	1.28 (1.08 to 1.52)	0.004	1.25 (1.05 to 1.48)	0.011
20–29 years	22 221 (68.4%)	519 (68.1%)	1.00		1.00
30–49 years	4770 (14.7%)	61 (8.0%)	0.82 (0.63 to 1.07)	0.14	1.00 (0.76 to 1.31)	0.98
Total number of deliveries
Single	8306 (25.6%)	126 (16.5%)	1.00		1.00
2–4	23 323 (71.8%)	614 (80.6%)	1.63 (1.35 to 1.97)	<0.001	1.45 (1.18 to 1.77)	<0.001
5+	872 (2.7%)	22 (2.9%)	1.17 (0.74 to 1.84)	0.51	0.98 (0.62 to 1.56)	0.93
Twins at some point
No	32 044 (98.6%)	754 (99.0%)	1.00
Yes	457 (1.4%)	8 (1.0%)	0.70 (0.35 to 1.41)	0.32
Time between deliveries
One delivery	8306 (25.6%)	126 (16.5%)	1.00
All <2 years	3883 (11.9%)	97 (12.7%)	1.57 (1.20 to 2.04)	0.001
All ≥2 years	15 463 (47.6%)	393 (51.6%)	1.63 (1.33 to 1.99)	<0.001
Mixture	4849 (14.9%)	146 (19.2%)	1.59 (1.25 to 2.01)	<0.001
Type of perineal wound
No wound	13 601 (41.8%)	265 (34.8%)	1.00		1.00
All episiotomy	8852 (27.2%)	239 (31.4%)	1.32 (1.11 to 1.58)	0.002	1.22 (1.01 to 1.46)	0.035
At least one third-degree tear	150 (0.5%)	2 (0.3%)	0.90 (0.22 to 3.62)	0.88	0.81 (0.20 to 3.24)	0.76
No perineal tears (lacerations only)	9898 (30.5%)	256 (33.6%)	1.53 (1.29 to 1.82)	<0.001	1.31 (1.10 to 1.57)	0.003

CS, caesarean section; SVD, spontaneous vaginal delivery; UI, urinary incontinence.