Incidence of and risk factors for perineal trauma: a prospective observational study

Table 2 Unadjusted and adjusted ORs for association of characteristics and OASIS in women with a singleton vaginal delivery

Characteristics	Unadjusted	Adjusted OR
Characteristics	OR (95% CI)	(95% CI)
Nulliparity	1.0	1.0
Multiparity	0.33 (0.22, 0.50)*	0.52 (0.30, 0.90)*
Community (FMU or home)	1.0	1.0
Hospital	3.30 (1.44, 7.56)*	NE
Age group (years)¹
<21	1.0
21–30	1.14 (0.44, 2.92)	NE
31–40	1.55 (0.61, 3.90)	NE
>40	1.11 (0.26, 4.76)	NE
Birthing pool²	1.21 (0.67, 2.18)	1.28 (0.50, 2.11)
Epidural³	1.78 (1.22, 2.59)*	0.56 (0.33, 0.93)*
Spontaneous (non-operative) delivery	1.0	1.0
Ventouse	2.71 (1.59, 4.61)*	2.03 (0.96, 4.30)
Forceps	6.56 (4.28, 10.1)*	4.43 (2.02, 9.71)*
Directed pushing⁴	2.66 (1.68, 4.23)*	1.15 (0.62, 2.14)
Delivery position lying down	1.0	1.0
Delivery position upright	0.47 (0.32, 0.68)*	1.17 (0.68, 2.02)
Perineum touched⁵	0.86 (0.52, 1.40)	0.91 (0.53, 1.56)
Delivery technique hands on either or both perineum and head	1.0	1.0
Delivery technique Off/off	0.48 (0.27, 0.86)*	0.77 (0.39, 1.52)
Occipito posterior or Occipito transverse	1.0	1.0
Occipito anterior	0.41 (0.22, 0.77)*	0.69 (0.33, 1.42)
Duration 2^nd stage (log mins)	2.10 (1.74, 2.54)*	1.49 (1.13, 1.98)*
Episiotomy⁶	2.33 (1.57, 3.46)*	0.64 (0.36, 1.15)
Shoulder dystocia⁷	7.35 (3.40, 16.0)*	NE
Birth weight (g)	1.001 (1.001, 1.001)*	1.001 (1.001, 1.001)*

Reference category: * = statistically significant (p < 0.05); 1 = age group 20 or below; 2 = birthing pool not used; 3 = no epidural used; 4 = undirected pushing; 5 = Perineum not touched; 6 = no episiotomy; 7 = no shoulder dystocia; NE = not estimated as < 10 participants with or without characteristic. Maternal birth position was categorised as: upright if semi-recumbent/sitting, all fours/kneeling forward, birth stool, kneeling/standing or squatting, or lying down if left or right lateral, lithotomy or supine. For spontaneous birth, delivery technique was categorised as ‘off’ both head and perineum, or ‘on’ if hands were placed either on the baby’s head or perineum or both. Pushing was categorised as directed if pushing was directed for all or some of the time or undirected if no directions were given.

ISSN: 1471-2393