TABLE 2.
Preterm Birth Rates According to Selected Individual-Level Risk Factors Within Lifetime Residential Environment Groups: Illinois Transgenerational Birthfile, Cook County, 1989–1991
| Residential Environment at Birth/Adulthood |
||||||||
| Maternal Characteristics | 1st/1st Quartile, PTB Per 100 Live Births | 1st/2nd Quartile, PTB Per 100 Live Births | 1st/3rd Quartile, PTB Per 100 Live Births | 1st/4th Quartile, PTB Per 100 Live Births | 1st/2nd Quartile, RR (95% CI) | 1st/3rd Quartile, RR (95% CI) | 1st/4th Quartile, RR (95% CI) | |
| Birth weight, g | ||||||||
| < 2500 | 23.4 | 20.0 | 19.7 | 17.9 | 0.9 (0.7, 1.0) | 0.8 (0.6, 1.1) | 0.8 (0.5, 1.2) | |
| ≥ 2500 | 18.5 | 15.9 | 15.0 | 11.9 | 0.8 (0.8, 0.9) | 0.8 (0.7, 0.9) | 0.6 (0.5, 0.8) | |
| Age, y | ||||||||
| < 20 | 19.1 | 19.2 | 16.3 | 19.8 | 1.0 (0.9 1.2) | 0.8 (0.6, 1.1) | 1.0 (0.7, 1.6) | |
| 20–29 | 18.1 | 15.5 | 14.4 | 10.7 | 0.8 (0.7, 0.9) | 0.9 (0.7, 0.9) | 0.6 (0.5, 0.8) | |
| 30–35 | 20.1 | 15.4 | 16.9 | 12.9 | 0.8 (0.7, 0.9) | 0.8 (0.7, 1.0) | 0.6 (0.4, 0.9) | |
| Education, y | ||||||||
| < 12 | 20.9 | 20.1 | 19.5 | 16.7 | 1.0 (0.9, 1.1) | 0.9 (0.7, 1.2) | 0.8 (0.5, 1.2) | |
| 12 | 18.2 | 15.7 | 16.5 | 12.9 | 0.8 (0.7, 1.0) | 0.9 (0.8, 1.0) | 0.7 (0.5, 1.0) | |
| > 12 | 14.5 | 13.4 | 13.0 | 10.6 | 0.9 (0.8, 1.1) | 0.9 (0.7, 1.1) | 0.7 (0.5, 1.0) | |
| Parity | ||||||||
| High (≥ 3 previous pregnancies) | 21.7 | 18.7 | 17.2 | 11.4 | 0.9 (0.8, 1.0) | 0.8 (0.7, 0.9) | 0.5 (0.4 0.8) | |
| Low (1–2 previous pregnancies) | 17.3 | 14.8 | 13.2 | 12.9 | 0.9 (0.8, 1.0) | 0.8 (0.7, 0.9) | 0.7 (0.6, 1.0) | |
| Zero | 16.5 | 14.6 | 17.4 | 12.6 | 0.9 (0.8, 1.0) | 1.1 (0.9, 1.3) | 0.8 (0.5, 1.1) | |
| Marital status | ||||||||
| Married | 13.2 | 12.2 | 12.0 | 9.0 | 0.9 (0.8, 1.1) | 0.9 (0.7, 1.1) | 0.7 (0.5, 1.0) | |
| Not married | 19.5 | 17.4 | 17.7 | 15.5 | 0.9 (0.8, 1.0) | 0.9 (0.8, 1.0) | 0.8 (0.6, 1.0) | |
| Prenatal care | ||||||||
| None or inadequate | 17.9 | 16.8 | 14.3 | 16.1 | 0.9 (0.8, 1.1) | 0.8 (0.6, 1.0) | 0.9 (0.6, 1.3) | |
| Intermediate or adequate | 12.0 | 9.1 | 7.7 | 5.7 | 0.8 (0.7, 0.9) | 0.6 (0.5, 0.8) | 0.5 (0.3, 0.7) | |
| Adequate or better | 35.2 | 30.6 | 32.1 | 26.8 | 0.9 (0.8, 1.0) | 0.9 (0.8, 1.1) | 0.8 (0.6, 1.0) | |
| Cigarette smoker | ||||||||
| Yes | 22.6 | 21.1 | 20.7 | 20.5 | 0.9 (0.8, 1.1) | 0.9 (0.7, 1.1) | 0.9 (0.6, 1.3) | |
| No | 17.3 | 14.4 | 14.1 | 10.7 | 0.8 (0.8, 0.9) | 0.8 (0.7, 0.9) | 0.6 (0.5, 0.8) | |
Note. CI = confidence interval; PTB = preterm birth rates; RR = rate ratio.