Characteristic | 2004–2005 | 2006–2007 | 2008–2009 | 2010–2011 | p Value | Pooled 2004–2011 |
---|---|---|---|---|---|---|
Women with first vaginal birth | ||||||
n | 40 995 | 41 664 | 42 684 | 42 738 | 168 081 | |
Distribution of risk groups* | ||||||
Low risk (%) | 72.3 | 71.6 | 71.6 | 71.1 | 0.002 | 71.6 |
High risk (%) | 27.7 | 28.4 | 28.4 | 28.9 | 28.4 | |
Low risk, risk scores <1.85 | ||||||
Episiotomy use (%) | 50.4 | 47.4 | 41.9 | 36.9 | ≤0.001 | 44.1 |
Change in episiotomy use (uOR, 95% CI) | 1 (reference) | 0.88 (0.86 to 0.91) | 0.71 (0.69 to 0.73) | 0.58 (0.56 to 0.60) | ||
OASIS (% (n)) | 0.8 (242) | 1.1 (336) | 1.1 (348) | 1.3 (396) | ≤0.001 | (1322) |
OASIS with episiotomy (% (n)) | 0.7 (111) | 1.3 (189) | 1.6 (210) | 2.1 (236) | 1.4 (746) | |
OASIS without episiotomy (% (n)) | 0.9 (131) | 0.9 (147) | 0.8 (138) | 0.8 (160) | 0.9 (576) | |
Change in OASIS (uOR, 95% CI) | 1 (reference) | 1.38 (1.17 to 1.63) | 1.40 (1.19 to 1.65) | 1.60 (1.37 to 1.88) | ||
High risk, risk scores >1.85 | ||||||
Episiotomy use (%) | 72.8 | 72.7 | 71.5 | 66.6 | ≤0.001 | 70.8 |
Change in episiotomy use (uOR, 95% CI) | 1 (reference) | 0.99 (0.94 to 1.05) | 0.94 (0.88 to 0.99) | 0.74 (0.70 to 0.79) | ||
OASIS (% (n)) | 2.6 (297) | 2.6 (309) | 2.6 (311) | 2.7 (336) | 0.89 | 2.6 (1253) |
OASIS with episiotomy (% (n)) | 2.4 (201) | 2.7 (230) | 2.7 (237) | 3.0 (249) | 2.7 (917) | |
OASIS without episiotomy (% (n)) | 3.1 (96) | 2.4 (79) | 2.1 (74) | 2.1 (87) | 2.4 (336) | |
Change in OASIS (uOR, 95% CI) | 1 (reference) | 1.00 (0.85 to 1.17) | 0.98 (0.83 to 1.15) | 1.04 (0.89 to 1.22) | ||
Women with at least one prior vaginal birth | ||||||
n | 52 274 | 53 338 | 55 180 | 55 765 | 216 557 | |
Distribution of risk groups* | ||||||
Low risk (%) | 75.2 | 76.2 | 77.2 | 76.7 | ≤0.001 | 76.4 |
High risk (%) | 24.8 | 23.8 | 22.8 | 23.3 | 23.6 | |
Low risk, risk scores <2.50 | ||||||
Episiotomy use (%) | 8.4 | 6.9 | 5.3 | 4.0 | ≤0.001 | 6.1 |
Change in episiotomy use (uOR, 95% CI) | 1 (reference) | 0.80 (0.76 to 0.84) | 0.60 (0.57 to 0.64) | 0.45 (0.43 to 0.48) | ||
OASIS (% (n)) | 0.1 (34) | 0.1 (59) | 0.2 (68) | 0.2 (83) | 0.001 | 0.1 (244) |
OASIS with episiotomy (% (n)) | 0.2 (7) | 0.9 (26) | 1.2 (26) | 1.5 (25) | 0.8 (84) | |
OASIS without episiotomy (% (n)) | 0.1 (27) | 0.1 (33) | 0.1 (42) | 0.1 (58) | 0.1 (160) | |
Change in OASIS (uOR, 95% CI) | 1 (reference) | 1.68 (1.10 to 2.56) | 1.85 (1.22 to 2.79) | 2.24 (1.51 to 3.35) | ||
High risk, risk scores >2.50 | ||||||
Episiotomy use (%) | 15.0 | 13.4 | 11.6 | 9.6 | ≤0.001 | 12.4 |
Change in episiotomy use (uOR, 95% CI) | 1 (reference) | 0.88 (0.82 to 0.94) | 0.75 (0.69 to 0.80) | 0.60 (0.56 to 0.65) | ||
OASIS (% (n)) | 0.3 (45) | 0.5 (64) | 0.5 (58) | 0.6 (76) | 0.04 | 0.5 (243) |
OASIS with episiotomy (% (n)) | 0.5 (10) | 1.6 (27) | 1.4 (20) | 2.9 (36) | 1.5 (93) | |
OASIS without episiotomy (% (n)) | 0.3 (35) | 0.3 (37) | 0.3 (38) | 0.3 (40) | 0.3 (150) | |
Change in OASIS (uOR, 95% CI) | 1 (reference) | 1.46 (0.99 to 2.14) | 1.33 (0.90 to 1.96) | 1.69 (1.17 to 2.45) |
χ2-test or logistic regression analyses.
*The best thresholds to maximise sensitivity and specificity; 1.85 (sensitivity 49% and specificity 72%) in women with first vaginal births including women admitted for first vaginal birth after a prior caesarean section and 2.50 (sensitivity 50% and specificity 76%) and in women with at least one prior birth.
uOR, unadjusted OR.