Table 1.
Population characteristics of 1,490 African-American mothers from the Boston Birth Cohort
| Maternal characteristics a | Mothers of TB (Controls) | Mothers of sPTB (Cases) | P-value b | |
|---|---|---|---|---|
|
| ||||
| n | 1033 | 457 | ||
| Age at delivery (years), mean ± SD | 28.3±0.20 | 28.5±0.32 | 0.603 | |
| Gestational age at delivery (weeks), mean ± SD | 39.6±0.04 | 33.3±0.17 | <0.001 | |
| Age at delivery (years), n (%) | 0.400 | |||
| <20 | 115 (11.1) | 53 (11.6) | ||
| 20–29.9 | 503 (48.7) | 208 (45.5) | ||
| 30–34.9 | 239 (23.1) | 102 (22.3) | ||
| ≥ 35.0 | 176 (17.1) | 94 (20.6) | ||
| Pre-pregnancy BMI (kg/m2), n (%) | ||||
| <18.5 | 36 (3.5) | 18 (3.9) | 0.189 | |
| 18.5–24.9 | 445 (43.1) | 192 (42.0) | ||
| 25.0–29.9 | 261 (25.3) | 136 (29.8) | ||
| ≥ 30 | 233 (22.6) | 82 (17.9) | ||
| Missing | 58 (5.6) | 29 (6.3) | ||
| Marital status, n (%) | Married | 347 (33.6) | 124 (27.1) | 0.013 |
| Parity, n (%) | 0 | 439 (42.4) | 191 (41.8) | 0.096 |
| 1 | 297 (28.8) | 112 (24.5) | ||
| ≥ 2 | 297 (28.8) | 154 (33.7) | ||
| Education level, n (%) | College or above | 406 (39.3) | 160 (35.1) | 0.130 |
| Smoking during pregnancy, n (%) | ||||
| Never | 853 (82.6) | 337 (73.7) | <0.001 | |
| Former smoker | 76 (7.4) | 41 (9.0) | ||
| Current smoker | 97 (9.4) | 78 (17.1) | ||
| Missing | 7 (0.7) | 1 (0.2) | ||
| Alcohol drinking during pregnancy | 74 (7.2) | 43 (9.4) | 0.062 | |
| Maternal lifetime stress | Low | 395 (38.2) | 144 (31.5) | 0.001 |
| Average | 533 (51.6) | 239 (52.3) | ||
| High | 105 (10.2) | 74 (16.2) | ||
| Maternal stress during pregnancy | ||||
| Low | 384 (37.2) | 148 (32.4) | 0.071 | |
| Average | 459 (44.4) | 200 (43.8) | ||
| High | 187 (18.1) | 108 (23.6) | ||
| Missing | 3 (0.3) | 1 (0.2) | ||
| Support from the baby’s father | No or little | 177 (17.1) | 102 (22.3) | 0.001 |
| Fairy or more | 791 (76.6) | 310 (67.8) | ||
| Missing | 65 (6.3) | 45 (9.8) | ||
| Support from family/friends | No or little | 76 (7.3) | 40 (8.8) | 0.003 |
| Fairy or more | 910 (88.2) | 377 (82.4) | ||
| Missing | 47 (4.5) | 40 (8.8) | ||
| Newborn sex: Male | 526 (50.9) | 238 (52.1) | 0.680 | |
TB: Term birth; sPTB: Spontaneous preterm birth; BMI: Body mass index; SD: Standard deviation
a
n (%) are shown in the table, if not specified.
b
Each variable was compared between sPTB cases and TB controls, using chi-squared and t-test, respectively, for categorical and continuous variables.