Table 4.

Odds ratios of factors associated with residual volume ≥ 750 ml, stratified by mode of birth (spontaneous or instrumental)

Spontaneous birth n = 1323
	Unadjusted OR	95% CI		p value	Adjusted OR4	95% CI		p value
Pudendal nerve block	0.92	0.43	1.95	0.83	0.81	0.36	1.81	0.61
Epidural/spinal analgesia	2.09	0.78	5.55	0.14	2.06	0.75	5.67	0.16
Episiotomy	0.52	0.23	1.18	0.12	0.49	0.21	1.13	0.10
Birth unit1	0.55	0.21	1.42	0.21	0.47	0.17	1.28	0.14
Instrumental birth2 n = 1283
	Unadjusted OR	95% CI		p value	Adjusted OR4	95% CI		p value
Pudendal nerve block	0.93	0.41	2.11	0.86	0.94	0.41	2.16	0.88
Epidural/ spinal analgesia	1.34	0.26	6.94	0.73	1.79	0.32	10.05	0.51
Episiotomy	1.11	0.33	3.77	0.87	1.11	0.32	3.85	0.87
Birth unit1	0.50	0.20	1.26	0.14	0.46	0.18	1.20	0.11

¹Unit 1 (Rikshospitalet) compared with Unit 2 (Ullevål). ²Vacuum and/or forceps extraction. ³Number of women included in the analysis. ⁴Multivariable model, epidural/spinal analgesia, episiotomy and birth unit were included. OR: odds ratio; CI: confidence interval