Table 1 Preterm birth (PTB) rates by maternal characteristic, Québec, 1989-2006
|  | All PTB % | Medically indicated % | PPROM* % | Spontaneous†% | Total births |
|---|---|---|---|---|---|
Maternal age | Â | Â | Â | Â | Â |
   < 20 years | 8.4 | 1.9 | 2.1 | 4.3 | 56,647 |
   20-24 years | 6.7 | 1.7 | 2.0 | 3.0 | 260,848 |
   25-29 years | 5.8 | 1.6 | 1.8 | 2.4 | 487,831 |
   30-34 years | 5.7 | 1.8 | 1.8 | 2.2 | 373,906 |
   35-39 years | 6.9 | 2.4 | 2.2 | 2.3 | 130,525 |
   ≥ 40 years | 8.6 | 3.5 | 2.6 | 2.5 | 19,979 |
Grand multiparity | 6.1 | 1.7 | 1.7 | 2.7 | 6,010 |
Period | Â | Â | Â | Â | Â |
   1989-1993 | 5.9 | 1.6 | 1.7 | 2.7 | 454,300 |
   1994-1997 | 6.3 | 1.8 | 1.9 | 2.6 | 321,884 |
   1998-2001 | 6.4 | 1.9 | 2.1 | 2.5 | 276,252 |
   2002-2006 | 6.5 | 2.1 | 2.1 | 2.3 | 277,301 |
Comorbidity | Â | Â | Â | Â | Â |
   Systemic | 8.7 | 4.1 | 2.2 | 2.4 | 323,433 |
   Localized | 10.9 | 4.9 | 2.9 | 3.0 | 241,580 |
   No | 4.7 | 0.5 | 1.7 | 2.4 | 839,539 |
Total | 6.2 | 1.8 | 1.9 | 2.5 | 1,329,737 |