TABLE 1—
Characteristics of African American and White Women and Risk Ratios (RRs) for Preterm Birth: Women With Pregnancies Initiated April 1996–August 2000
| African American Women (n = 724) | White Women (n = 1174) | |||||
| No. | % Preterm | RR (95% CI) | No. | % Preterm | RR (95% CI) | |
| Mother’s education, y | ||||||
| < 12 | 176 | 8.0 | 0.6 (0.3, 1.1) | 166 | 14.5 | 1.0 (0.6, 1.6) |
| 12a | 277 | 13.4 | 1.0 | 276 | 14.9 | 1.0 |
| > 12 | 271 | 13.3 | 1.0 (0.6, 1.5) | 732 | 9.6 | 0.6 (0.4, 0.9) |
| Mother’s age at 24 weeks’ gestation, y | ||||||
| 16–19 | 149 | 8.1 | 0.7 (0.4, 1.3) | 112 | 11.6 | 1.0 (0.5, 1.7) |
| 20–29a | 434 | 11.1 | 1.0 | 568 | 12.5 | 1.0 |
| ≥ 30 | 141 | 19.2 | 1.7 (1.1, 2.7) | 494 | 10.7 | 0.9 (0.6, 1.2) |
| Parity | ||||||
| 0a | 328 | 10.1 | 1.0 | 562 | 9.1 | 1.0 |
| 1 | 213 | 13.2 | 1.3 (0.8, 2.1) | 359 | 14.8 | 1.6 (1.1, 2.3) |
| ≥ 2 | 178 | 14.0 | 1.4 (0.9, 2.3) | 248 | 12.5 | 1.4 (0.9, 2.1) |
| Missing information | 5 | 5 | ||||
| Marital status | ||||||
| Not marrieda | 535 | 11.0 | 1.0 | 314 | 12.4 | 1.0 |
| Married | 186 | 14.5 | 1.3 (0.9, 2.0) | 860 | 11.2 | 0.9 (0.6, 1.3) |
| Missing information | 3 | 0 | ||||
| Height, inches | ||||||
| < 62 | 71 | 14.1 | 1.2 (0.7, 2.3) | 107 | 15.0 | 1.2 (0.8, 2.0) |
| 62 to < 68a | 512 | 11.5 | 1.0 | 872 | 12.0 | 1.0 |
| ≥ 68 | 113 | 13.3 | 1.2 (0.7, 2.0) | 172 | 7.6 | 0.6 (0.4, 1.1) |
| Missing information | 28 | 23 | ||||
| Prepregnancy BMI | ||||||
| Underweight (< 19.8) | 90 | 8.9 | 0.8 (0.4, 1.7) | 190 | 11.1 | 1.0 (0.6, 1.5) |
| Normal weight (19.8–26.0)a | 280 | 11.1 | 1.0 | 622 | 11.4 | 1.0 |
| Overweight (> 26.0–29.0) | 80 | 8.8 | 0.8 (0.4, 1.7) | 115 | 11.3 | 1.0 (0.6, 1.7) |
| Obese (> 29.0) | 229 | 14.9 | 1.3 (0.9, 2.1) | 205 | 12.7 | 1.1 (0.7, 1.7) |
| Missing information | 45 | 42 | ||||
| Poverty index, % of federal poverty threshold | ||||||
| < 50 | 93 | 11.8 | 1.0 (0.5, 2.0) | 33 | 12.1 | 1.1 (0.4, 2.8) |
| 50 to < 100 | 170 | 15.9 | 1.3 (0.7, 2.3) | 137 | 13.9 | 1.2 (0.8, 2.0) |
| 100 to < 200 | 202 | 10.4 | 0.9 (0.5, 1.6) | 235 | 11.5 | 1.0 (0.7, 1.5) |
| ≥ 200a | 141 | 12.1 | 1.0 | 678 | 11.2 | 1.0 |
| Missing information | 118 | 91 | ||||
| BV | ||||||
| No BVa | 554 | 12.3 | 1.0 | 1026 | 11.3 | 1.0 |
| BV detected | 141 | 11.4 | 0.9 (0.6, 1.5) | 87 | 11.5 | 1.0 (0.6, 1.9) |
| Missing information | 29 | 61 | ||||
| Clinic site | ||||||
| University care site | 335 | 16.4 | 2.0 (1.3, 3.0) | 900 | 12.6 | 1.6 (1.0, 2.4) |
| Public health departmenta | 389 | 8.2 | 1.0 | 274 | 8.0 | 1.0 |
| Alcohol use during pregnancy, drinks/week | ||||||
| < 5 drinks/weeka | 660 | 11.7 | 1.0 | 1111 | 11.5 | 1.0 |
| ≥ 5 drinks/week | 5 | 40.0 | 3.4 (1.1, 10.2) | 11 | 0 | . . .b |
| Missing information | 59 | 52 | ||||
| Smoked during months 1–6 of pregnancy, cigarettes/day | ||||||
| Nonea | 541 | 11.5 | 1.0 | 807 | 10.8 | 1.0 |
| 1–9 cigarettes/day | 86 | 14.0 | 1.2 (0.7, 2.2) | 147 | 13.6 | 1.3 (0.8, 2.0) |
| 10–19 cigarettes/day | 19 | 15.8 | 1.4 (0.5, 4.0) | 99 | 16.2 | 1.5 (0.9, 2.4) |
| ≥ 20 cigarettes/day | 7 | 14.3 | 1.2 (0.2, 7.8) | 43 | 11.6 | 1.1 (0.5, 2.5) |
| Missing information | 71 | 78 | ||||
Notes. CI = confidence interval; BMI = body mass index; BV = bacterial vaginosis.
aReference category.
bToo few cases to calculate risk ratio.