Table 2 Risk of OASI in first, second and third live, singleton, vaginal births at term
Variables | 1st births1 | 2nd births2 | 3rd births2 | ||||||
|---|---|---|---|---|---|---|---|---|---|
Model 1 | Model 2 | Model 3 | Model 1 | Model 2 | Model 3 | Model 1 | Model 2 | Model 3 | |
n = 436,670 | (n = 412,442) | (n = 412,442) | n = 379,787 | (n = 350,986) | (n = 350,982) | (n = 140,102) | (n = 128,668) | (n = 128,668) | |
Adj OR (95% CI) | Adj OR (95% CI) | Adj OR (95% CI) | Adj OR (95% CI) | Adj OR (95% CI) | Adj OR (95% CI) | Adj OR (95% CI) | Adj OR (95% CI) | Adj OR (95% CI) | |
Maternal age (years) | |||||||||
< 25 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 |
25–29 | 1.75 (1.69–1.82) | 1.66 (1.59–1.72) | 1.56 (1.50–1.62) | 2.05 (1.83–2.29) | 1.78 (1.58–2.01) | 1.73 (1.53–1.95) | 1.29 (0.83–1.99) | 1.09 (0.67–1.77) | 1.07 (0.66–1.73) |
30–34 | 2.05 (1.98–2.13) | 1.94 (1.86–2.02) | 1.74 (1.67–1.81) | 2.84 (2.55–3.16) | 2.30 (2.04–2.59) | 2.18 (1.93–2.46) | 1.90 (1.25–2.89) | 1.60 (1.00–2.56) | 1.51 (0.94–2.42) |
≥ 35 | 2.01 (1.92–2.11) | 1.95 (1.85–2.05) | 1.64 (1.56–1.73) | 3.18 (2.84–3.55) | 2.54 (2.24–2.87) | 2.32 (2.05–2.63) | 2.64 (1.74–4.01) | 2.16 (1.34–3.46) | 1.97 (1.23–3.16) |
Year of delivery | |||||||||
1999–2004 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 |
2005–2011 | 0.88 (0.86–0.90) | 0.89 (0.87–0.91) | 0.88 (0.86–0.90) | 0.88 (0.84–0.91) | 0.85 (0.82–0.89) | 0.85 (0.81–0.89) | 0.77 (0.68–0.86) | 0.79 (0.70–0.89) | 0.80 (0.71–0.90) |
Education | |||||||||
Elementary: 9 ≤ years | 0.83 (0.78–0.87) | 0.84 (0.79–0.89) | 0.92 (0.83–1.02) | 0.92 (0.84–1.02) | 1.02 (0.83–1.26) | 1.01 (0.82–1.25) | |||
High school | 1 | 1 | 1 | 1 | 1 | 1 | |||
College or university | 1.08 (1.05–1.12) | 1.10 (1.07–1.13) | 1.01 (0.96–1.06) | 1.03 (0.98–1.08) | 0.97 (0.85–1.11) | 0.97 (0.85–1.11) | |||
Country/Region of birth | |||||||||
Sweden | 1 | 1 | 1 | 1 | 1 | 1 | |||
Asia | 1.66 (1.58–1.74) | 1.58 (1.50–1.65) | 1.40 (1.28–1.54) | 1.36 (1.24–1.49) | 1.43 (1.15–1.78) | 1.40 (1.13–1.74) | |||
Africa | 2.01 (1.85–2.20) | 1.96 (1.79–2.14) | 1.76 (1.50–2.06) | 1.71 (1.45–2.00) | 2.14 (1.58–2.88) | 2.05 (1.52–2.77) | |||
Other | 0.93 (0.89–0.97) | 0.93 (0.88–0.97) | 0.95 (0.87–1.03) | 0.95 (0.87–1.04) | 0.92 (0.73–1.17) | 0.94 (0.74–1.18) | |||
Smoking in early pregnancy | |||||||||
No | 1 | 1 | 1 | 1 | 1 | 1 | |||
Yes | 0.81 (0.76–0.86) | 0.81 (0.76–0.86) | 0.88 (0.78–0.98) | 0.87 (0.77–0.97) | 0.96 (0.75–1.22) | 0.93 (0.73–1.18) | |||
BMI | |||||||||
Low: <18.5 | 1.23 (1.14–1.33) | 1.22 (1.13–1.31) | 1.28 (1.08–1.52) | 1.28 (1.08–1.51) | 0.71 (0.35–1.43) | 0.71 (0.35–1.44) | |||
Normal weight: 18.5–24.9 | 1 | 1 | 1 | 1 | 1 | 1 | |||
Overweight: 25–29.9 | 0.96 (0.93–0.99) | 0.95 (0.92–0.99) | 1.00 (0.94–1.05) | 0.99 (0.94–1.05) | 0.92 (0.80–1.06) | 0.92 (0.80–1.06) | |||
Obese: ≥ 30 | 0.90 (0.85–0.94) | 0.90 (0.86–0.95) | 0.96 (0.89–1.03) | 0.96 (0.89–1.04) | 0.79 (0.65–0.97) | 0.79 (0.64–0.97) | |||
Infant birthweight (g) | |||||||||
< 3000 | 1 | 1 | 1 | 1 | 1 | 1 | |||
3000–3499 | 1.70 (1.61–1.81) | 1.69 (1.60–1.80) | 1.45 (1.25–1.67) | 1.44 (1.25–1.67) | 1.02 (0.68–1.53) | 1.02 (0.68–1.54) | |||
3500–3999 | 2.98 (2.81–3.16) | 2.88 (2.72–3.05) | 2.53 (2.20–2.91) | 2.50 (2.17–2.87) | 2.40 (1.64–3.51) | 2.38 (1.62–3.48) | |||
4000–4499 | 5.08 (4.78–5.40) | 4.69 (4.41–4.98) | 4.25 (3.69–4.90) | 4.09 (3.55–4.72) | 3.97 (2.70–5.83) | 3.84 (2.61–5.65) | |||
≥ 4500 | 8.51 (7.86–9.20) | 7.62 (7.04–8.25) | 7.39 (6.34–8.61) | 7.01 (6.01–8.17) | 8.17 (5.48–12.16) | 7.70 (5.16–11.49) | |||
Presentation | |||||||||
Occiput anterior | 1 | 1 | 1 | 1 | 1 | 1 | |||
Occiput posterior | 1.89 (1.78–2.00) | 1.43 (1.35–1.51) | 1.92 (1.74–2.12) | 1.59 (1.44–1.76) | 2.00 (1.55–2.59) | 1.58 (1.22–2.06) | |||
Breech | 0.87 (0.76–0.99) | 1.06 (0.93–1.22) | 1.20 (0.72–2.02) | 1.26 (0.75–2.12) | 1.34 (0.33–5.40) | 1.34 (0.33–5.42) | |||
Other | 1.11 (1.04–1.18) | 1.03 (0.97–1.11) | 1.24 (1.09–1.41) | 1.22 (1.07–1.38) | 1.72 (1.30–2.28) | 1.70 (1.29–2.25) | |||
History of OASI in 1st pregnancy3 | |||||||||
No | 1 | 1 | |||||||
Yes | 4.38 (4.08–4.70) | 4.38 (4.09–4.70) | |||||||
History of cesarean section 1st pregnancy3 | |||||||||
No | 1 | 1 | |||||||
Yes | 7.14 (6.77–7.53) | 5.46 (5.14–5.80) | |||||||
History of OASI in 2nd pregnancy4 | |||||||||
No | 1 | 1 | |||||||
Yes | 8.92 (7.28–10.90) | 8.62 (7.01–10.61) | |||||||
History of cesarean section 2nd pregnancy4 | |||||||||
No | 1 | 1 | |||||||
Yes | 3.29 (2.45–4.41) | 2.93 (2.18–3.95) | |||||||
Diabetes | |||||||||
No | 1 | 1 | 1 | ||||||
Yes | 0.98 (0.79–1.21) | 1.35 (1.04–1.73) | 0.98 (0.48–2.02) | ||||||
Epidural analgesia | |||||||||
No | 1 | 1 | 1 | ||||||
Yes | 0.93 (0.90–0.95) | 1.09 (1.03–1.15) | 1.10 (0.93–1.29) | ||||||
Episiotomy | |||||||||
No | 1 | 1 | 1 | ||||||
Yes | 0.89 (0.87–0.92) | 1.04 (0.96–1.13) | 1.34 (1.01–1.77) | ||||||
Vacuum extraction or forceps | |||||||||
No | 1 | 1 | 1 | ||||||
Yes | 2.87 (2.80–2.95) | 2.82 (2.63–3.02) | 4.07 (3.33–4.99) | ||||||