Table 3.
Adjusteda HRs (95% CIs) for preterm birth and gestational age-specific TTHM exposure averages by race and ancestry.
| TTHM (μg/L) | 1st Trimester | 2nd Trimester | 4-Week risk sets | Pregnancy average |
|---|---|---|---|---|
| All races (n = 2,813) | ||||
| < 40 | 1.00 | 1.00 | 1.00 | 1.00 |
| 40 to < 60 | 1.02 (0.92–1.13) | 0.87 (0.77–0.99) | 1.00 (0.87–1.15) | 0.92 (0.82–1.02) |
| ≥ 60 | 1.00 (0.88–1.14) | 0.82 (0.71–0.94) | 1.13 (0.95–1.35) | 0.85 (0.74–0.97) |
| Per 10 μg/L | 0.98 (0.95–1.02) | 0.95 (0.92–0.99) | 1.01 (0.97–1.06) | 0.95 (0.91–0.99) |
| Caucasians (n = 1,429) | ||||
| < 40 | 1.00 | 1.00 | 1.00 | 1.00 |
| 40 to < 60 | 0.97 (0.84–1.12) | 0.93 (0.77–1.11) | 0.97 (0.79–1.18) | 0.92 (0.79–1.06) |
| ≥ 60 | 1.04 (0.87–1.24) | 0.86 (0.71–1.05) | 1.14 (0.90–1.45) | 0.81 (0.67–0.99) |
| Per 10 μg/L | 0.99 (0.94–1.05) | 0.95 (0.90–1.00) | 1.04 (0.97–1.10) | 0.96 (0.91–1.03) |
| African American (n = 607) | ||||
| < 40 | 1.00 | 1.00 | 1.00 | 1.00 |
| 40 to < 60 | 1.27 (1.00–1.60) | 0.73 (0.56–0.96) | 0.78 (0.57–1.07) | 0.95 (0.74–1.20) |
| ≥ 60 | 1.13 (0.84–1.52) | 0.62 (0.46–0.84) | 1.00 (0.69–1.45) | 0.77 (0.57–1.05) |
| Per 10 μg/L | 1.01 (0.93–1.10) | 0.89 (0.82–0.96) | 0.98 (0.89–1.08) | 0.90 (0.81–0.99) |
| Hispanic (n = 541) | ||||
| < 40 | 1.00 | 1.00 | 1.00 | 1.00 |
| 40 to < 60 | 0.97 (0.75–1.24) | 1.07 (0.80–1.43) | 1.59 (1.15–2.21) | 0.87 (0.68–1.12) |
| ≥ 60 | 0.86 (0.63–1.17) | 1.07 (0.78–1.46) | 1.63 (1.09–2.43) | 1.00 (0.73–1.36) |
| Per 10 μg/L | 0.95 (0.87–1.04) | 1.04 (0.96–1.14) | 1.05 (0.95–1.17) | 1.01 (0.91–1.11) |
| Asian (n = 233) | ||||
| < 40 | 1.00 | 1.00 | 1.00 | 1.00 |
| 40 to < 60 | 0.94 (0.65–1.34) | 0.65 (0.42–1.02) | 0.80 (0.49–1.29) | 0.89 (0.62–1.26) |
| ≥ 60 | 0.77 (0.49–1.22) | 0.72 (0.44–1.20) | 0.68 (0.35–1.29) | 0.86 (0.54–1.37) |
| Per 10 μg/L | 0.90 (0.79–1.03) | 0.95 (0.82–1.09) | 0.88 (0.74–1.04) | 0.86 (0.74–1.01) |
a
HRs were adjusted for infant sex, marital status, adequacy of prenatal care, maternal age, maternal race/ethnicity, maternal education, parity, maternal smoking, prenatal care source of payment, conception season, birth season, per-capita income, previous preterm or SGA infant, previous trimester TTHM exposure, and the presence of one or more maternal disease factors including lung disease, diabetes, eclampsia, hydramnios, chronic hypertension, pregnancy-related hypertension, incompetent cervix, renal disease, uterine bleeding, and inappropriate maternal weight gain/loss.