Table 4. Demographic and pregnancy characteristics for all women with an initial third- or fourth-degree tear who had a second vaginal birth (nested case-control study).
| Second pregnancy characteristic | Repeat 3rd / 4th degree tear n (%) (N = 149) |
No repeat 3rd / 4th degree tear n (%) (N = 2105) |
P-value | Unadjusted OR (99%CI) | Adjusted OR (99%CI)a |
|---|---|---|---|---|---|
| Age | |||||
| Missing = 0 | |||||
| Mean (SD) | 31.5 (4.6) | 30.1 (5.3) | 0.002* | 1.05 (1.01–1.10) | 1.06 (1.00–1.12) |
| Smoking | |||||
| Missing = 104 (4.6) | |||||
| Non smoker | 124 (86.7) | 1535 (76.5) | 1 | 1 | |
| Smoker | 7 (4.9) | 260 (12.4) | 0.005* | 0.33 (0.12–0.92) | 0.61 (0.21–1.80) |
| Ex-smoker | 12 (8.4) | 212 (10.1) | 0.253 | 0.70 (0.31–1.56) | 0.54 (0.19–1.54) |
| Deprivation | |||||
| Missing = 8 (0.4) | |||||
| Most deprived (1–5) | 80 (53.7) | 1010 (48.2) | 0.661 | 1.08 (0.70–1.67) | 1.20 (0.69–2.09) |
| Least deprived (6–10) | 69 (46.3) | 1087 (51.6) | 1 | 1 | |
| Diabetes | |||||
| Missing = 223 (9.9) | |||||
| Yes | 2 9(1.4) | 1872 (99.0) | 0.634 | 1.43 (0.21–9.82) | 1.05 (0.69–15.96) |
| No | 138 (98.6) | 19 (1.0) | 1 | 1 | |
| BMI | |||||
| Missing = 577 (25.6) | |||||
| Median (IQR) | 24.9 (6.4) | 24.7 (6.4) | 0.789 | 1.00 (0.95–1.05) | 0.99 (0.93–1.05) |
| Mode of delivery | |||||
| Missing = 0 | |||||
| SVD | 145 (97.3) | 1989 (94.5) | 0.602 | 1 | 1 |
| Forceps | 4 (2.7) | 72 (3.4) | 0.998 | 0.76 (0.20–2.92) | 0.55 (0.07–4.15) |
| Ventouse | 0 | 33 (1.6) | 0.999 | — | — |
| Vaginal breech | 0 | 11 (0.5) | — | — | |
| Weight of baby (grams) | |||||
| Missing = 2 (0.1) | |||||
| <4500g | |||||
| ≥4500g | 139 (93.3) | 2045 (97.2) | 0.008* | 1 | 1 |
| 10 (6.7) | 58 (2.8) | 2.54 (1.02–6.30) | 3.27 (1.11–9.60) | ||
| Gestation at birth | |||||
| (weeks) | |||||
| Missing = 0 | |||||
| Median (IQR) | 40 (1.0) | 40 (2.0) | 0.335 | 1.02 (0.97–1.07) | 1.01 (0.95–1.08) |
| Episiotomy | |||||
| Missing = 59 (2.6) | |||||
| Yes | 27 (18.2) | 456 (22.3) | 0.254 | 0.78 (0.44–1.37) | 0.88 (0.43–1.84) |
| No | 121 (81.8) | 1591 (77.7) | 1 | 1 | |
| Induction of labour | |||||
| Missing = 5 (0.2) | |||||
| None | |||||
| ARM only | 119 (79.9) | 1664 (79.2) | 1 | 1 | |
| ARM +PG | 10 (6.7) | 82 (3.9) | 0.125 | 1.71 (0.70–4.18) | 1.81 (0.60–5.44) |
| 20 (13.4) | 354 (16.9) | 0.343 | 0.79 (0.42–1.50) | 0.68 (0.29–1.58) | |
| Position at delivery | |||||
| Missing = 139 (6.2) | |||||
| OA | 125 (90.6) | 1831 (87.0) | 1 | 1 | |
| OP | 7 (5.1) | 67 (3.2) | 0.297 | 1.53 (0.54–4.38) | 2.06 (0.62–6.82) |
| OT | 5 (3.6) | 49 (2.3) | 0.401 | 1.50 (0.44–5.13) | 0.84 (0.06–12.22) |
| Other | 1 (0.7) | 30 (1.4) | 0.482 | 0.49 (0.04–6.77) | — |
aCovariates included in the multivariate model were age, smoking, deprivation, diabetes, BMI, mode of delivery, weight of baby, gestation, episiotomy, induction of labour and position at delivery (all in second pregnancy)
Missing data not included in the proportions presented.
*denotes statistical significance.