Table 4. Adjusted risk of OASIS for multiparous women delivering vaginally and multiparous women grouped by birthweight between 1997 and 2007 in Finland (Logistic regression analyses).
| Characteristic/outcome | Multiparae | Multiparae with <3000 g infant | Multiparae with 3000–4000 g infant | Multiparae with >4000 g infant |
| N | n = 288,391 | n = 25,184 | n = 196,593 | n = 66,614 |
| Mode of delivery | ||||
| Vaginal delivery | 1 | 1 | 1 | 1 |
| Breech | 0.79 (0.20–3.17) | – | 1.02 (0.25–4.12) | – |
| Forceps | 10.48 (2.53–43.35) | – | 23.34 (5.55–98.14) | – |
| Vacuum assistance | 4.23 (3.21–5.58) | 6.50 (0.76–55.37) | 4.29 (2.92–6.30) | 4.14 (2.78–6.17) |
| Maternal age (year) | ||||
| ≥29 | 1 | 1 | 1 | 1 |
| 30–39 | 1.25 (1.03–1.50) | 0.30 (0.08–1.15) | 1.43 (1.10–1.85) | 1.14 (0.86–1.51) |
| ≥40 | 1.52 (1.04–2.24) | 1.83 (0.38–8.76) | 1.65 (0.96–2.81) | 1.33 (0.74–2.41) |
| Birth weight (g) | ||||
| <3000 | 1 | – | – | – |
| 3000–4000 | 2.59 (1.48–4.51) | |||
| >4000 | 5.73 (3.27–10.05) | |||
| 1Length of active 2nd stage (min) | ||||
| ≤15 | 1 | 1 | 1 | 1 |
| 16–30 | 2.96 (2.11–4.14) | 1.39 (0.17–11.43) | 3.23 (2.09–5.26) | 2.72 (1.63–4.54) |
| 31–45 | 4.33 (2.78–6.74) | – | 5.32 (2.94–9.62) | 3.46 (1.75–6.84) |
| 46–60 | 3.03 (1.48–6.20) | – | 2.31 (0.70–7.64) | 3.75 (1.50–9.40) |
| ≥61 | 7.24 (4.37–12.00) | – | 10.08 (5.24–19.37) | 5.29 (2.38–11.77) |
| Episiotomy | 2.04 (1.68–2.48) | 0.45 (0.05–3.73) | 2.41 (1.85–3.15) | 1.75 (1.31–2.35) |
| Epidural analgesia | 1.50 (1.24–1.82) | 1.70 (0.52–5.58) | 1.44 (1.10–1.87) | 1.57 (1.18–2.08) |
| Smoking status | ||||
| Non-smoking | 1 | 1 | 1 | 1 |
| Given up smoking | 0.23 (0.06–0.91) | – | 0.21 (0.03–1.50) | 0.27 (0.04–1.90) |
| Smoking | 0.87 (0.64–1.18) | 1.30 (0.40–4.23) | 0.80 (0.54–1.19) | 0.94 (0.55–1.58) |
1
Length of active 2nd stage of birth adjusted only for 2004–2007.