Table 5 Risk of preterm birth according to maternal age (years) and mode of labor among singletons and multiples. Lombardy, Italy, 2007–2017
| Â | Maternal age group | |||||
|---|---|---|---|---|---|---|
< 20 | 20–24 | 25–29 | 30–34 | 35–39 | ≥40 | |
Singletons a | ||||||
 Spontaneous | ||||||
  N (%) | 283 (4.3) | 1285 (3.2) | 3973 (2.8) | 7410 (2.7) | 6344 (2.9) | 1978 (3.3) |
  OR | 1.57 (1.39–1.78) | 1.14 (1.07–1.22) | 1.00 | 0.98 (0.94–1.02) | 1.05 (1.01–1.10) | 1.20 (1.14–1.27) |
  aOR | 1.38 (1.22–1.57) | 1.05 (0.99–1.13) | 1.00 | 1.03 (0.99–1.07) | 1.10 (1.06–1.15) | 1.22 (1.15–1.29) |
 Induced | ||||||
  N (%) | 146 (2.2) | 959 (2.4) | 3105 (2.2) | 6430 (2.4) | 6444 (3.0) | 2552 (4.3) |
  OR | 1.02 (0.86- 1.21) | 1.09 (1.01–1.17) | 1.00 | 1.09 (1.04–1.14) | 1.38 (1.32–1.44) | 2.02 (1.92–2.13) |
  aOR | 0.90 (0.76–1.07) | 1.00 (0.93–1.08) | 1.00 | 1.15 (1.10–1.20) | 1.43 (1.37–1.50) | 1.96 (1.86–2.08) |
Multiples b | ||||||
 Spontaneous | ||||||
  N (%) | 23 (38.3) | 96 (26.5) | 456 (25.7) | 1041 (23.3) | 909 (20.9) | 338 (17.8) |
  OR | 2.05 (1.21–3.47) | 1.19 (0.93–1.51) | 1.14 (1.00–1.29) | 1.00 | 0.87 (0.79–0.96) | 0.72 (0.63–0.82) |
  aOR | 1.76 (1.02–3.10) | 1.13 (0.87–1.45) | 1.12 (0.98–1.28) | 1.00 | 0.88 (0.79–0.97) | 0.72 (0.63–0.83) |
 Induced | ||||||
  N (%) | 19 (31.7) | 146 (40.2) | 624 (35.1) | 1544 (34.5) | 1657 (38.0) | 856 (45.2) |
  OR | 0.88 (0.51–1.52) | 1.28 (1.03–1.60) | 1.03 (0.92–1.15) | 1.00 | 1.17 (1.07–1.27) | 1.57 (1.40–1.75) |
  aOR | 1.01 (0.58–1.78) | 1.35 (1.08–1.71) | 1.05 (0.93–1.18) | 1.00 | 1.15 (1.05–1.26) | 1.48 (1.32–1.66) |