Table 3 Multivariate conditional logistic regression analysis for obstetric anal sphincter injury among multiparous women

Non-modifiable variables

Birthweight quartiles

292

   < 3300 g

44

Reference

Reference

  3300–3659 g

71

3.42

1.24–9.46

5.58

1.56–20.0

  3660–4039 g

80

4.91

1.70–14.2

6.90

1.86–25.7

   ≥ 4040 g

109

7.13

2.57–19.8

11.4

3.10–42.2

Modifiable variables

  Amniotomy

44

3.44

1.64–7.23

3.76

1.45–9.76

  Augmentation with oxytocin

107

3.19

1.82–5.59

3.70

1.79–7.67

  Episiotomy^a

101

2.88

1.66–5.00

2.64

1.36–5.14