Authors | Sample Size/ Characteristics considering only vaginal births | Method of LA assessment | Reported LA tear rate % (n) | Predictors of Any LevatorAni Muscle Tear | |||||||
Maternal age | Instrumental delivery | Anal sphincter laceration | Prolonged second stage | Episiotomy | Infant Size | Infant head circumference | |||||
Kearney et al. 2006 | N = 160 Case control with cases incontinent and controls continent recruited 9 - 12 months post birth between 1997 - 2001 (USA) | MRI | 18.1% (29 of 160) | p = 0.001 mean age = 32.8 vs 29.3 years for those with and without LA tear respectively | VacuumNS forceps OR = 14.7 | OR = 8.1 | mean = 92.5 min (no injury) mean = 170.5 min (LA injury) (p = 0.001) | 3.1 OR | NS | not reported | |
Dietz & Lanzarone 2005 | N = 39 All comers recruited prospective to birth (Austria) | 3D trans- labial ultra- sound | 36% (14 of 39) | mean age = 31.6 NS (p = 0.10) | p = 0.07 | Factors not specifically identified but reported as not significant | |||||
Valsky et al. 2009 | N = 210 All comers recruited 23 - 72 hours post birth between 2006 - 2008 (Jerusalem) | 3D trans- perineal ultra sound | 18.6% (39 of 210) | Mean age = 25.8 ± 4.3 NS (p = 0.104) | VacuumNS | not reported | mean = 69.01 (no injury) mean = 87.0 min (LA injury) OR = 2.27 p = 0.027 | NS | mean = 3128 gm (no injury) mean = 3309.41 gm (LA injury) p = 0.024 | mean = 33.77 cm (no injury) mean = 34.24 cm (LA injury) OR = 3.343 p = 0.040 | |
Shek & Dietz 2010 | N = 240 All comers recruited prospective to birth 2005-2008. Post birth dates study measures varied. (Australia) | 4D trans- labial ultra- sound | 13% (32 of 240) | Mean age = 25.9 significance not reported | Forceps OR = 4.2 vacuum NS | not reported | NS | OR = 2.34 | NS | NS | |
Cassadó Garriga et al. 2011 | N = 120 Case Control with cases (n = 60) forceps delivery and controls (n = 60) vaginal birth without episiotomy or perineal tears studied 40 to 120 days post birth (Spain) | 4D introital ultra- sound | 61.7% (37 of 60) cases 13.3% (8 of 60) controls | Mean age = 30.2 ± 3.6 vs 29.4 ± 4.1 for cases and controls respectively. significance not reported | Forceps OR 10.47 (CI 4.2 - 25.9) | not reported | not reported | not reported | NS | not reported | |
Chan et al. 2012 | N = 263 All comers recruited prospective to birth, 2009 - 2010, studied 8 weeks postpartum (Hong Kong) | 3D trans- labial ultra- sound | 71.4% (10 of 14)- forceps 33.3% (16 of 48)- vacuum 15.4% (31 of 201)- spontaneous vaginal birth | mean age 30.6 ± 3.9 NS (p = 0.82) | Forceps p < 0.001 Vacuum p < 0.001 any operative vaginal delivery Significance remained in multivariate analysis OR 3.09 (CI 1.46 - 6.52) | not reported | p = 0.05 in multivariate analysis p < 0.001 in univariate analysis. | All but 10 women in the sample had episiotomies, so lack of varianceprohibited analysis of independent contribution | NS (p = 0.47) in multivariate analysis p = 0.04 in univariate analysis | not included in multivariate analysis, substantial amount of missing data p = 0.01 in univariate analysis | |