Skip to main content

Advertisement

Table 3 Unadjusted and adjusted risk ratios and 95 % CI for OASIS among nulliparous and parous

From: Birth position and obstetric anal sphincter injury: a population-based study of 113 000 spontaneous births

  Nulliparous (n = 44 942) Parous (n = 65 486)
Unadjusted risk ratio Adjusted risk ratio* Unadjusted risk ratio Adjusted risk ratio*
95 % CI 95 % CI 95 % CI 95 % CI
Total
Sitting 1.00 1.00 1.00 1.00
Lithotomy 1.33 (1.21-1.46) 1.17 (1.06-1.29) 2.19 (1.83-2.62) 1.66 (1.35-2.05)
Lateral 0.79 (0.69-0.91) 0.79 (0.68-0.92) 0.82 (0.67-1.01) 0.84 (0.66-1.06)
Knee 0.88 (0.73-1.06) 0.88 (0.71-1.09) 0.78 (0.60-1.00) 0.81 (0.58-1.11)
Birth seat 1.05 (0.92-1.21) 1.05 (0.90-1.22) 1.37 (1.07-1.74) 1.36 (1.03-1.80)
Supine 0.89 (0.68-1.16) 0.91 (0.67-1.22) 0.84 (0.60-1.18) 0.84 (0.55-1.30)
Squatting 0.81 (0.49-1.36) 0.66 (0.36-1.24) 1.79 (0.95-3.35) 2.16 (1.15-4.07)
Standing 0.69 (0.36-1.33) 0.71 (0.34-1.49) 0.49 (0.20-1.18) 0.40 (0.10-1.61)
All four 1.03 (0.59-1.78) 1.12 (0.62-2.05) 1.18 (0.53-2.64) 0.95 (0.30-2.96)
Maternal age (years)
 <35 1.00 1.00 1.00 1.00
 >35 1.25 (1.12-1.39) 1.21 (1.08-1.36) 1.13 (0.99-1.30) 1.12 (0.96-1.32)
Head circumference
 <35 1.00 1.00 1.00 1.00
 >35 1.76 (1.62-1.92) 1.42 (1.29-1.57) 1.95 (1.65-2.31) 1.52 (1.23-1.88)
Birth weight
 <4000 g 1.00 1.00 1.00 1.00
 >4000 g 2.16 (1.96-2.39) 1.69 (1.52-1.88) 2.54 (2.22-2.91) 1.86 (1.57-2.21)
Length of second stage
 <90 min 1.00 1.00 1.00 1.00
 >90 min 1.36 (1.25-1.47) 1.15 (1.05-1.26) 2.44 (1.98-3.01) 1.93 (1.53-2.45)
Length of gestation (weeks)
 <40 1.00 1.00 1.00 1.00
 >40 1.50 (1.38-1.64) 1.20 (1.09-1.31) 1.64 (1.42-1.87) 1.25 (1.04-1.49)
Epidural analgesia
 No 1.00 1.00 1.00 1.00
 Yes 1.02 (0.94-1.10) 0.82 (0.74-0.90) 1.28 (1.11-1.47) 1.01 (0.88-1.24)
Non-occiput anterior presentation
 No 1.00 1.00 1.00 1.00
 Yes 1.48 (1.20-1.82) 1.30 (1.01-1.68) 1.92 (1.47-2.51) 1.51 (1.10-2.05)
Oxytocin augmentation
 No 1.00 1.00 1.00 1.00
 Yes 1.31 (1.21-1.42) 1.21 (1.09-1.35) 1.33 (1.15-1.53) 0.93 (0.78-1.12)
  1. *Adjusted for all other variables in table + time in years + in-hospital delivery unit