Table 1.
Demographics of preterm births in Detroit, Michigan study area, May to September, 1991 to 2001
| N | % | |
| Total | 9053 | 100 |
| Month | ||
| May | 1918 | 21.2 |
| June | 1944 | 21.5 |
| July | 1903 | 21.0 |
| August | 1754 | 19.4 |
| September | 1534 | 16.9 |
| Year (two equal time periods) | ||
| 1991–1995 | 4708 | 56.2 |
| 1996–2000 | 3670 | 43.8 |
| Maternal race | ||
| White | 2443 | 27.0 |
| Black | 6433 | 71.1 |
| Other | 177 | 1.9 |
| Maternal smoking status | ||
| Non-smoker | 6621 | 73.1 |
| Smoker | 2345 | 25.9 |
| Missing | 87 | 1.0 |
| Level of prenatal care | ||
| Prenatal care | 5037 | 55.6 |
| Late or no prenatal care | 2960 | 32.7 |
| Missing | 1056 | 11.7 |
| Maternal age | ||
| 16–19 years | 1782 | 19.7 |
| 20–29 years | 4821 | 53.2 |
| ≥30 years | 2450 | 27.1 |
| Maternal education | ||
| Less than high school | 3485 | 38.5 |
| High school or higher | 5451 | 60.2 |
| Missing | 117 | 1.3 |