Document Classification

Section Type: RESULTS

Text: Anal sphincter injury was strongly and independently associated with first vaginal birth (RR 39. 2, 95 % CI 5. 4-282. 5), median episiotomy (adjusted RR 9. 6, 95 % CI 3. 2-28. 5), forceps delivery (adjusted RR 12. 3, 95 % CI 3. 0-50. 4) and vacuum-assisted delivery (adjusted RR 7. 4, 95 % CI 1. 9-28. 5) but not with birth weight (adjusted RR for nirth weight 4000 g or more : 1. 4, 95 % CI 0. 6-3. 0) or length of the second stage of labour (adjusted RR for second stage 1. 5 hours or longer compared with less than 0. 5 hours : 1. 2, 95 % CI 0. 5-2. 7).