. Author manuscript; available in PMC: 2012 Aug 8.

Published in final edited form as: Int Urogynecol J Pelvic Floor Dysfunct. 2008 Nov 5:10.1007/s00192-008-0754-0. doi: 10.1007/s00192-008-0754-0

Table 2.

Risk factors for anal sphincter tears

Logistic Regression Model Variables	Odds Ratio	95% Confidence Interval
Age > 21 years	ref
Age 17-20 years	0.9	0.7-1.2
Age ≤ 16 years	1.1	0.8-1.5
Vacuum delivery	1.5	1.1-2.2
Shoulder dystocia	2.9	1.6-5.3
Birth weight > 4000g	3.1	2.1-4.4
Forceps delivery	3.5	2.7-4.5
Episiotomy	7.6	5.4-10.7