Crude rates of preterm birth among singleton live births to non-Hispanic black and non-Hispanic white women in Canada and the United States, 2004–2006
| Characteristic | Crude rate in Canada, % (95% CI) | Crude rate in US, % (95% CI) | ||||
|---|---|---|---|---|---|---|
| Black | White | Black–white difference | Black | White | Black–white difference | |
| Maternal age, yr | ||||||
| < 20 | 9.6 (5.0 to 14.2) | 8.1 (7.0 to 9.3) | 1.5 (−3.4 to 6.3) | 12.8 (12.6 to 13.0) | 9.8 (9.7 to 9.9) | 3.0 (2.8 to 3.2) |
| 20–24 | 6.3 (4.2 to 8.4) | 6.3 (5.8 to 6.7) | 0.0 (−2.0 to 2.2) | 12.1 (12.0 to 12.2) | 8.5 (8.4 to 8.5) | 3.6 (3.5 to 3.8) |
| 25–29 | 8.0 (6.2 to 9.8) | 5.7 (5.4 to 6.0) | 2.3 (0.4 to 4.1) | 12.1 (12.0 to 12.2) | 7.7 (7.6 to 7.7) | 4.4 (4.3 to 4.6) |
| 30–34 | 8.8 (7.1 to 10.6) | 5.8 (5.5 to 6.1) | 3.1 (1.3 to 4.8) | 13.0 (12.9 to 13.2) | 7.5 (7.4 to 7.5) | 5.6 (5.4 to 5.8) |
| 35–39 | 11.2 (8.4 to 14.1) | 5.9 (5.4 to 6.3) | 5.4 (2.6 to 8.2) | 15.1 (14.9 to 15.4) | 8.2 (8.1 to 8.2) | 7.0 (6.7 to 7.2) |
| ≥ 40 | 16.0 (10.1 to 21.9) | 8.6 (7.3 to 9.9) | 7.4 (1.3 to 13.4) | 17.6 (17.1 to 18.1) | 9.6 (9.5 to 9.8) | 7.9 (7.4 to 8.5) |
| Live birth order | ||||||
| First-born | 10.1 (8.5 to 11.8) | 7.2 (7.0 to 7.4) | 2.9 (1.3 to 4.6) | 12.3 (12.2 to 12.4) | 8.8 (8.7 to 8.8) | 3.6 (3.4 to 3.7) |
| Second | 8.0 (6.2 to 9.9) | 4.7 (4.4 to 5.0) | 3.3 (1.5 to 5.2) | 11.8 (11.7 to 11.9) | 7.1 (7.1 to 7.2) | 4.7 (4.6 to 4.8) |
| Third or later | 8.2 (6.5 to 10.0) | 5.4 (5.1 to 5.8) | 2.8 (1.0 to 4.5) | 14.0 (13.9 to 14.2) | 8.2 (8.2 to 8.3) | 5.8 (5.7 to 6.0) |
| Sex of infant | ||||||
| Female | 9.9 (8.3 to 11.4) | 5.5 (5.3 to 5.8) | 4.3 (2.8 to 5.9) | 12.7 (12.6 to 12.8) | 7.6 (7.6 to 7.7) | 5.1 (5.0 to 5.2) |
| Male | 8.1 (6.7 to 9.4) | 6.4 (6.2 to 6.7) | 1.6 (0.3 to 2.9) | 12.8 (12.7 to 12.8) | 8.5 (8.5 to 8.6) | 4.2 (4.1 to 4.3) |
| Maternal education, no. of years | ||||||
| < 12 | 7.7 (5.5 to 10.0) | 7.0 (6.4 to 7.5) | 0.8 (−1.5 to 3.1) | 14.1 (13.9 to 14.2) | 10.2 (10.1 to 10.3) | 3.9 (3.7 to 4.0) |
| 12–15 | 9.3 (8.1 to 10.6) | 6.1 (5.9 to 6.4) | 3.2 (1.9 to 4.5) | 12.6 (12.5 to 12.7) | 8.5 (8.4 to 8.5) | 4.1 (4.0 to 4.2) |
| ≥ 16 | 8.6 (6.3 to 10.8) | 5.4 (5.1 to 5.7) | 3.2 (1.0 to 5.4) | 10.8 (10.7 to 11.0) | 6.8 (6.7 to 6.8) | 4.1 (3.9 to 4.2) |
| Marital status | ||||||
| Unmarried | 9.5 (8.0 to 11.0) | 6.6 (6.3 to 6.9) | 2.9 (1.4 to 4.5) | 13.2 (13.2 to 13.3) | 9.6 (9.5 to 9.6) | 3.7 (3.6 to 3.8) |
| Married | 8.4 (7.1 to 9.8) | 5.7 (5.5 to 5.9) | 2.8 (1.4 to 4.1) | 11.5 (11.4 to 11.6) | 7.6 (7.5 to 7.6) | 4.0 (3.8 to 4.1) |
| Paternal information | ||||||
| Not missing | 8.8 (7.7 to 9.9) | 6.0 (5.8 to 6.1) | 2.8 (1.7 to 3.9) | 10.8 (10.5 to 11.1) | 7.8 (7.7 to 7.8) | 3.0 (2.7 to 3.4) |
| Missing | 10.4 (7.1 to 13.8) | 7.7 (6.4 to 8.9) | 2.8 (−0.9 to 6.4) | 12.0 (11.9 to 12.1) | 8.9 (8.7 to 9.1) | 3.1 (2.9 to 3.3) |
| Maternal nativity* | ||||||
| Native born | 8.3 (6.3 to 10.2) | 6.1 (5.9 to 6.3) | 2.2 (0.2 to 4.1) | 13.1 (13.0 to 13.2) | 8.1 (8.1 to 8.2) | 5.0 (4.9 to 5.1) |
| Foreign born | 9.2 (8.0 to 10.4) | 4.9 (4.4 to 5.4) | 4.2 (2.9 to 5.6) | 9.6 (9.3 to 9.9) | 6.1 (5.9 to 6.3) | 3.5 (3.1 to 3.8) |
Note: CI = confidence interval.
↵* For US, maternal nativity available only for births in 2004 (n = 1 493 259).