Table 2.
Association of first and second birth factors with planned caesarean section at second birth following OASI at first birth
| Planned CS | Planned vaginal | p | crOR | aOR | ||
|---|---|---|---|---|---|---|
| n = 1447 | n = 4933 | |||||
| (22.7%) | (77.3%) | |||||
| Country of birth* | Asian | 202 (14.0) | 979 (19.9) | <0.01 | 0.66 (0.56, 0.77) | 0.69 (0.58, 0.84) |
| Non Asian | 1236 (85.4) | 3923 (79.5) | Reference | |||
| FIRST BIRTH FACTORS | ||||||
| Diabetes | Yes | 70 (4.8) | 200 (4.1) | 0.19 | 1.20 (0.91, 1.59) | 1.17 (0.84, 1.63) |
| No | 1377 (95.2) | 4733 (95.9) | Reference | |||
| Hypertension | Yes | 133 (9.2) | 430 (8.7) | 0.58 | 1.06 (0.86, 1.30) | 1.00 (0.79, 1.27) |
| No | 1314 (90.8) | 4503 (91.3) | Reference | |||
| Gestation* (weeks) | <37 | 34 (2.4) | 84 (1.7) | <0.01 | 1.49 (0.99, 2.23) | 1.39 (0.87, 2.22) |
| 37-38 | 160 (11.1) | 621 (12.6) | 0.95 (0.78, 1.15) | 0.81 (0.65, 0.99) | ||
| 39-40 | 782 (54.0) | 2870 (58.2) | Reference | Reference | ||
| ≥41 | 471 (32.5) | 1357 (27.5) | 1.27 (1.12, 1.45) | 1.42 (1.22, 1.65) | ||
| Induction/augmentation | Yes | 1064 (73.5) | 3352 (68.0) | <0.01 | 1.31 (1.15, 1.49) | 1.11 (0.96, 1.30) |
| No | 383 (26.5) | 1581 (32.0) | Reference | |||
| Epidural/spinal or GA | Yes | 915 (63.2) | 2185 (44.3) | <0.01 | 2.16 (1.92, 2.44) | 1.73 (1.50, 2.00) |
| No | 532 (36.8) | 2748 (55.7) | Reference | |||
| Birth mode | Instrumental | 815 (56.3) | 2209 (44.8) | <0.01 | 1.59 (1.41, 1.79) | 1.16 (0.99, 1.35) |
| Non-instr | 632 (43.7) | 2724 (55.2) | Reference | |||
| Episiotomy | Yes | 718 (49.6) | 2121 (43.0) | <0.01 | 1.31 (1.16, 1.47) | 1.12 (0.98, 1.29) |
| No | 729 (50.4) | 2812 (57.0) | Reference | |||
| OASIS | Fourth | 267 (18.5) | 203 (4.1) | <0.01 | 5.27 (4.35, 6.70) | 4.95 (4.00, 6.13) |
| Third/Unknown** | 1180 (81.5) | 4730 (95.9) | Reference | |||
| Birthweight (kg)* | <3.0 | 130 (9.0) | 504 (10.2) | <0.01 | 1.10 (0.88, 1.37) | 0.99 (0.77, 1.27) |
| 3.0- < 3.5 | 417 (28.8) | 1772 (35.9) | Reference | Reference | ||
| 3.5- < 4.0 | 562 (38.8) | 1918 (38.9) | 1.25 (1.08, 1.44) | 1.22 (1.04, 1.43) | ||
| ≥4.0 | 337 (23.3) | 739 (15.0) | 1.94 (1.64, 2.29) | 1.66 (1.38, 2.01) | ||
| Interpregnancy interval | <1 | 291 (20.1) | 1094 (22.2) | 0.04 | 0.91 (0.76, 1.09) | 0.95 (0.77, 1.17) |
| (years) | 1- < 2 | 601 (41.5) | 2099 (42.6) | 0.98 (0.84, 1.15) | 1.03 (0.86, 1.22) | |
| 2- < 3 | 292 (20.2) | 999 (20.3) | Reference | Reference | ||
| ≥3 | 263 (18.2) | 740 (15.0) | 1.22 (1.00, 1.47) | 1.13 (0.91, 1.40) | ||
| SECOND PREGNANCY | ||||||
| Maternal age | <25 | 136 (9.4) | 593 (12.0) | <0.01 | 0.80 (0.65, 0.97) | 0.75 (0.60, 0.93) |
| 25-34 | 972 (67.2) | 3381 (68.5) | Reference | Reference | ||
| 35-40 | 309 (21.4) | 897 (18.2) | 1.20 (1.03, 1.39) | 1.13 (0.96, 1.33) | ||
| >40 | 30 (2.1) | 62 (1.3) | 1.68 (1.08, 2.62) | 1.42 (0.87, 2.31) | ||
| Diabetes | Yes | 93 (6.4) | 269 (5.5) | 0.16 | 1.19 (0.93, 1.52) | 0.99 (0.74, 1.33) |
| No | 1354 (93.6) | 4664 (94.5 | Reference | |||
| Hypertension | Yes | 53 (3.7) | 187 (3.8) | 0.82 | 0.97 (0.71, 1.32) | 0.78 (0.55, 1.12) |
| No | 1394 (96.3) | 4746 (96.2) | Reference | |||
| Gestation* (weeks) | <37 | 85 (5.9) | 168 (3.4) | <0.01 | 2.03 (1.55, 2.67) | 2.20 (1.64, 2.95) |
| 37-38 | 581 (4.02) | 888 (18.0) | 2.63 (2.31, 3.0) | 2.87 (2.49, 3.31) | ||
| 39-40 | 757 (52.3) | 3041 (61.7) | Reference | Reference | ||
| ≥41 | 24 (1.7) | 835 (16.9) | 0.12 (0.08, 0.18) | 0.11 (0.07, 0.16) | ||
| Year of second birth | 01-05 | 309 (21.4) | 1194 (24.2) | 0.03 | Reference | Reference |
| 06-08 | 515 (35.6) | 1774 (36.0) | 1.12 (0.96, 1.32) | 1.06 (0.89, 1.27) | ||
| 09-11 | 623 (43.0) | 1965 (39.8) | 1.22 (1.05, 1.43) | 1.19 (1.01, 1.42) |
*Missing data <0.7%, these categories may not total 100%.
**Third/Unknown contains 107 records for which OASI was ascertained by procedure coding for 3rd/4th degree tear, and hence degree (3rd or 4th) of tearing is unknown.
Adjusted for all variables presented in table.