Table 1.
Factors associated with OASI recurrence at second vaginal birth, 2001–2011
| OASI at 2nd birth | No OASI at 2nd birth | p | Cr ORs | Adj ORs with all risk factors in model | |||
|---|---|---|---|---|---|---|---|
| n = 276 | n = 4532 | ||||||
| (5.7%) | (94.3%) | ||||||
| Country of birth* | Asian | 47 (17.0) | 910 (20.2) | 0.23 | 0.82 [0.60, 1.13] | 0.89 (0.63, 1.26) | |
| Non Asian | 226 (81.9) | 3594 (79.3) | Reference | Reference | |||
| FIRST BIRTH FACTORS | |||||||
| Diabetes | Yes | 17 (6.2) | 174 (3.8) | 0.06 | 1.64 [0.98, 2.75] | 1.76 [1.03, 3.01] | |
| No | 259 (39.8) | 4358 (96.2) | Reference | Reference | |||
| Epidural/spinal/general | Yes | 109 (39.5) | 1993 (44.0) | 0.14 | 0.82 [0.64, 1.05] | 0.79 [0.59, 1.06] | |
| No | 167 (60.5) | 2539 (56.0) | Reference | Reference | |||
| Birth mode | Instrumental | 120 (43.5) | 2007 (44.3) | 0.79 | 0.97 (0.76, 1.24) | 1.04 [0.78, 1.40] | |
| Non Instrumental | 156 (56.5) | 2525 (55.7) | Reference | Reference | |||
| Episiotomy | Yes | 121 (43.8) | 1939 (42.8) | 0.73 | 1.04 [0.82, 1.33] | 1.13 [0.86, 1.50] | |
| No | 155 (56.2) | 2593 (57.2) | Reference | Reference | |||
| Birthweight(kg) | <3.0 | 29 (10.5) | 462 (10.2) | 0.34 | 1.08 [0.70, 1.66] | 1.40 [0.89, 2.19] | |
| 3.0 - <3.5 | 95 (34.4) | 1636 (36.1) | Reference | Reference | |||
| 3.5 - <4.0 | 119 (43.1) | 1749 (38.6) | 1.17 [0.89, 1.55] | 0.94 [0.70, 1.27] | |||
| ≥ 4.0 | 33 (12.0) | 685 (15.1) | 0.83 [0.55, 1.25] | 0.53 [0.34, 0.82] | |||
| Inter pregnancy interval (years)* | <1 | 50 (18.1) | 1020 (22.5) | 0.39 | 0.76 [0.52, 1.13] | 0.78 [0.52, 1.17) | |
| 1- < 2 | 126 (45.7) | 1926 (42.5) | 1.02 [0.74, 1.40] | 1.04 [0.75, 1.45) | |||
| 2- < 3 | 59 (21.4) | 919 (20.3) | Reference | Reference | |||
| ≥3 | 41 (14.9) | 666 (14.7) | 0.96 [0.64, 1.45] | 1.01 [0.66, 1.54] | |||
| SECOND BIRTH FACTORS | |||||||
| Mat age | <25 | 29 (10.5) | 550 (12.1) | 0.61 | 0.87 [0.58, 1.30] | 0.93 [0.61, 1.41] | |
| 25-34 | 189 (68.5) | 3110 (68.6) | Reference | Reference | |||
| ≥35 | 58 (21.0) | 872 (19.2) | 1.09 [0.81, 1.48] | 1.07 [0.78, 1.46] | |||
| Hypertension | Yes | 16 (5.8) | 161 (3.5) | 0.05 | 1.67 [0.99, 2.84] | 1.56 [0.90, 2.71] | |
| No | 260 (94.2) | 4371 (96.5) | Reference | Reference | |||
| Gestation (weeks)* | <37 | 4 (1.5) | 155 (3.4) | <0.01 | 0.36 [0.13, 0.99] | 0.73 [0.24, 2.19] | |
| 37-38 | 29 (10.5) | 840 (18.5) | 0.49 [0.33, 0.73] | 0.55 [0.36, 0.84] | |||
| 39-40 | 197 (71.4) | 2779 (61.3) | Reference | Reference | |||
| ≥41 | 46 (16.7) | 757 (16.7) | 0.86 [0.62, 1.19] | 0.72 [0.51, 1.02] | |||
| Induction/Augmentation | Yes | 143 (51.8) | 2428 (53.6) | 0.57 | 0.93 [0.73,1.19] | 0.95 [0.73, 1.24] | |
| No | 133 (48.2) | 2104 (46.3) | Reference | Reference | |||
| Epidural | Yes | 48 (17.4) | 892 (19.7) | 0.35 | 0.86 [0.62, 1.18] | 0.95 [0.66, 1.38] | |
| No | 228 (82.6) | 3640 (80.3) | Reference | Reference | |||
| Birth mode | Instrumental | 24 (8.7) | 289 (6.4) | 0.13 | 1.40 (0.91, 2.16) | 1.30 [0.80, 2.12] | |
| Non-instrumental | 252 (91.3) | 4243 (93.6) | Reference | Reference | |||
| Episiotomy | Yes | 68 (24.6) | 1180 (26.0) | 0.61 | 0.93 [0.70, 1.23] | 0.84 [0.62, 1.14] | |
| No | 208 (75.4) | 3352 (74.0) | Reference | Reference | |||
| Infant sex* | Male | 158 (57.3) | 2323 (51.3) | 0.05 | 1.27 [1.00, 1.63] | 1.12 [0.87, 1.44] | |
| Female | 118 (42.7) | 2208 (48.7) | Reference | Reference | |||
| Birthweight(kg)* | <3.0 | 14 (5.1) | 543 (12.0) | <0.01 | 0.54 [0.30, 0.96] | 0.56 [0.23, 1.06] | |
| 3.0 - <3.5 | 80 (29.0) | 1675 (37.0) | Reference | Reference | |||
| 3.5 - <4.0 | 107 (38.8) | 1653 (36.5) | 1.36 [1.01, 1.83] | 1.48 [1.08, 2.02] | |||
| ≥4.0 | 75 (27.2) | 658 (14.5) | 2.39 [1.72, 3.31] | 2.89 [1.98, 4.22] | |||
| Year of second birth | 01-05 | 68 (24.6) | 1098 (24.2) | 0.24 | Reference | Reference | |
| 06-08 | 87 (31.5) | 1643 (36.3) | 0.86 [0.62, 1.19] | 0.84 [0.60, 1.17] | |||
| 09-11 | 121 (43.8) | 1791 (39.5) | 1.09 [0.80, 1.48] | 1.07 [0.78, 1.47] | |||
*Missing data <0.7%, these categories may not total 100%.
Adjusted for all variables presented in table.