Table 4.

Regression of fetal parameters on PM_2.5 exposure levels*

Fetal parameters	Coefficient	95% Confidence Interval	p-value
BPD
Mean PM2.5 quartile*
Q2	−0.001	−0.098 to 0.096	0.985
Q3	0.040	−0.058 to 0.138	0.424
Q4	0.036	−0.063 to 0.135	0.474
HC
Mean PM2.5 quartile
Q2	−0.065	− 0.394 to 0.264	0.698
Q3	0.021	−0.311 to 0.353	0.901
Q4	0.102	−0.232 to 0.435	0.551
FL
Mean PM2.5 quartile
Q2	−0.057	− 0.140 to 0.024	0.168
Q3	−0.012	−0.093 to 0.070	0.780
Q4	0.007	−0.075 to 0.089	0.869
AC
Mean PM2.5 quartile
Q2	−0.216	− 0.583 to 0.151	0.248
Q3	0.063	−0.306 to 0.432	0.738
Q4	0.083	−0.291 to 0.457	0.663
U-EFW
Mean PM2.5 quartile
Q2	−1.02	−31.144 to 29.112	0.947
Q3	14.13	−16.749 to 45.015	0.370
Q4	32.59	0.559 to 64.628	0.046

BPD biparietal diameter; HC head circumference; FL fetal length; AC abdominal circumference; U-EFW ultrasound-estimated fetal weight; Reference category for PM_2.5 level is the first quartile; square of gestational age was omitted from the model; *reference category – first quartile

*Adjusted for mother’s age, body mass index, marital status, educational level, number of children, history of stillbirth, and history of miscarriage