Table 4.
Trimester-specific associations of NO2 exposure with measures of fetal growth.
| NO2 [difference (95% CI)] | Trend test (per 1-µg/m3 increase) | p-Value for trend | ||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Fetal growth parameter | n | 2nd quartile | 3rd quartile | 4th quartile | ||||||||
| Head circumference | ||||||||||||
| Second trimester (mm) | 6,625 | 0.16 (–0.25, 0.57) | –0.24 (–0.66, 0.17) | –0.23 (–0.69, 0.22) | –0.02 (–0.05, 0.02) | 0.36 | ||||||
| Third trimester (mm) | 6,723 | –0.40 (–1.00, 0.20) | –0.81 (–1.42, –0.20)* | –1.28 (–1.96, –0.61)** | –0.12 (–0.17, –0.06) | < 0.01 | ||||||
| Birth (cm) | 4,448 | 0.04 (–0.05, 0.13) | 0.02 (–0.07, 0.12) | 0.00 (–0.10, 0.11) | 0.00 (–0.01, 0.01) | 0.85 | ||||||
| Length | ||||||||||||
| First trimester (mm) | 1,541 | –0.10 (–1.11, 0.91) | 0.54 (–0.50, 1.57) | 0.06 (–1.08, 1.20) | 0.01 (–0.07, 0.08) | 0.87 | ||||||
| Second trimester (mm) | 6,646 | –0.08 (–0.20, 0.05) | –0.18 (–0.30, –0.05)* | –0.19 (–0.33, –0.06)* | –0.02 (–0.03, –0.01) | < 0.01 | ||||||
| Third trimester (mm) | 6,778 | –0.02 (–0.17, 0.13) | –0.09 (–0.24, 0.06) | –0.33 (–0.50, –0.16)** | –0.02 (–0.04, –0.01) | < 0.01 | ||||||
| Birth (cm) | 5,606 | –0.10 (–0.25, 0.05) | –0.01 (–0.17, 0.14) | –0.09 (–0.26, 0.09) | –0.01 (–0.02, 0.01) | 0.49 | ||||||
| Weight | ||||||||||||
| Second trimester (g) | 6,612 | –0.3 (–3.3, 2.6) | –1.4 (–4.4, 1.6) | 0.8 (–2.5, 4.1) | 0.1 (–0.2, 0.3) | 0.67 | ||||||
| Third trimester (g) | 6,751 | –3.7 (–15.8, 8.5) | –7.2 (–19.6, 5.1) | –14.2 (–28.0, –0.5* | –0.7 (–1.8, 0.5) | 0.25 | ||||||
| Birth (g) | 7,003 | 2.6 (–25.0, 30.2) | –18.6 (–46.7, 9.6) | –37.6 (–69.7, –5.6)* | –3.4 (–6.2, –0.6) | 0.02 | ||||||
| Values are regression coefficients and reflect the difference in fetal growth parameters for each quartile of NO2 exposure (averaged from conception until measurement) compared with the reference group (lowest quartile). Cutoff values for categorization of NO2 exposure are < 37.0, 37.0–40.9, 40.9–43.9, > 43.9 μg/m3 for first trimester, < 37.0, 37.0–40.5, 40.5–43.4, > 43.4 μg/m3 for second trimester, < 37.0, 37.0–39.8, 39.8–42.8, > 42.8 μg/m3 for third trimester, and < 37.2, 37.2–39.6, 39.6–42.2, > 42.2 μg/m3 for total pregnancy. Models are adjusted for gestational age and noise exposure at measurement, maternal age, body mass index, height, parity, ethnicity, education, folic acid supplementation use, smoking, alcohol consumption, paternal height, and fetal sex. Models with neonatal head circumference or length are additionally adjusted for postconceptional age (gestational age for measurements at birth or gestational age plus postnatal age for measurements at the child health center), and models with neonatal length are additionally adjusted for method of measurement. *p < 0.05. **p < 0.001. | ||||||||||||