Table 1.
Characteristics of mother-child pairs in the Boston Birth Cohort by PM2.5 level in the third trimester (n=1293)
| Variable, Number (%) | PM2.5 Level During Third Trimester | p-value | ||
|---|---|---|---|---|
|
| ||||
| Tertile 1 (3.79–9.57 μg/m3) | Tertile 2 (9.57–11.80 μg/m3) | Tertile 3 (11.80–28.81 μg/m3) | ||
| Number | 431 | 431 | 431 | |
| Maternal Characteristics | ||||
| Age at delivery, mean (SD) | 28.88 (6.76) | 28.39 (6.51) | 28.32 (6.78) | 0.41 |
| African American race | 191 (44.3%) | 182 (42.2%) | 188 (43.6%) | 0.82 |
| Married mothers | 140 (33.0%) | 155 (36.3%) | 124 (29.2%) | 0.09 |
| Low educational achievement* | 122 (28.4%) | 126 (29.3%) | 137 (32.0%) | 0.48 |
| Smoke during pregnancy | 43 (10.0%) | 44 (10.4%) | 47 (11.0%) | 0.90 |
| Alcohol intake during pregnancy | 35 (8.3%) | 31 (7.5%) | 27 (6.6%) | 0.67 |
| Maternal hypertensive disorder | 76 (17.6%) | 65 (15.1%) | 83 (19.3%) | 0.26 |
| Pre-pregnancy BMI (kg/m2), mean (SD) | 26.46 (6.41) | 26.37 (5.95) | 27.14 (6.43) | 0.16 |
| Children Characteristics | ||||
| SBP percentile, mean (SD) | 56.30 (26.28) | 57.35 (25.88) | 60.97 (25.78) | 0.02 |
| Boys | 209 (48.5%) | 216 (50.1%) | 205 (47.6%) | 0.75 |
| Nulliparous | 186 (43.3%) | 164 (38.1%) | 186 (43.2%) | 0.21 |
| Preterm birth | 122 (28.3%) | 98 (22.7%) | 133 (30.9%) | 0.02 |
| Low birth weight | 112 (26.0%) | 98 (22.7%) | 132 (30.6%) | 0.03 |
| Vaginal delivery | 279 (64.7%) | 270 (62.6%) | 280 (65.0%) | 0.74 |
| Gestational age in week, mean (SD) | 37.66 (3.32) | 38.14 (2.83) | 37.75 (3.09) | 0.06 |
| BMI z-score, mean (SD) | 0.62 (1.36) | 0.76 (1.24) | 0.97 (1.22) | <0.01 |
*
Low educational achievement defined as having the highest education “Middle school or below”
†
Abbreviations: PM2.5 = particulate matter ≤2.5 microns; SD = standard deviation; BMI = body mass index; SBP = systolic blood pressure; Ref = Reference group