Table 3.

Estimates of the effects of the NO₂ and O₃ and significant control variables on placental volume (n = 229).

Placental variable/ pollutant and SV	Log volume
	SB	p-Value	SB	95% CI
Model 1a (n = 228)
NO2	0.061	0.315	0.001	–0.001, 0.004
O3	0.016	0.790	0.005	–0.034, 0.044
GA	0.454	< 0.001	0.271	0.201, 0.341
Model 2b (n = 228)
NO2	0.070	0.246	0.002	–0.001, 0.004
O3	0.018	0.759	0.006	–0.033, 0.045
GA	0.459	< 0.001	0.274	0.204, 0.345
Model 3c (n = 222)
NO2	0.080	0.200	0.002	–0.001, 0.004
O3	0.007	0.909	0.002	–0.037, 0.042
GA	0.446	< 0.001	0.264	0.192, 0.336
Model 4d (n = 187)
NO2	0.031	0.658	0.001	–0.002, 0.003
O3	0.018	0.793	0.005	–0.035, 0.046
GA	0.433	< 0.001	0.248	0.171, 0.325
Note: CI, confidence intervals; GA, gestational age; Log, logarithm; NO2, nitrogen dioxide; O3, ozone; SB, standardized beta; SV, significant variable. aModel 1: Exposure to both pollutants, controlling for gestational age of fetus. bModel 2: Exposure to both pollutants, controlling for gestational age of fetus, body mass index (BMI), parity, smoking, and placental location. cModel 3: Exposure to both pollutants, controlling for gestational age of fetus, BMI, parity, smoking, placental location, maternal alcohol consumption, maternal age, maternal ethnicity, and maternal education level. dModel 4: Exposure to both pollutants, controlling for gestational age of fetus, BMI, parity, placental location, maternal alcohol consumption, maternal age, maternal ethnicity, and maternal education level.