BACKGROUND

Limited studies have examined the effect of prenatal exposure to particulate matter with diameter of <2.5 µm (PM2.5) and <1 μm (PM1) on fetal growth using ultrasound measurements with inconsistent results. No study has evaluated the joint effect of the indoor air pollution index and ambient particulate matter on fetal growth.

METHODS

We conducted a prospective birth cohort study in Beijing, China in 2018, including 4319 pregnant women. We estimated prenatal PM2.5 and PM1 exposure using a machine-learning method and calculated the indoor air pollution index based on individual interviews. Gender- and gestational age-adjusted Z-score of the abdominal circumference (AC), head circumference (HC), femur length (FL) and estimated fetal weight (EFW) was calculated and then undergrowth was defined. A generalized estimating equation was used to evaluate the individual and joint effect of indoor air pollution index, PM2.5 and PM1 on fetal Z-score and undergrowth parameters.

RESULTS

One unit increase in the indoor air pollution index was associated with -0.044 (95% CI: -0.087, -0.001) and -0.050 (95% CI: -0.094, -0.006) decrease in the AC and HC Z-scores, respectively. PM1 and PM2.5 were associated with decreased AC, HC, FL and EFW Z-scores, and higher risk of undergrowth. Compared with exposure to lower PM1 (≤ median) and no indoor air pollution, those exposed to higher PM1 (> median) and indoor air pollution had decreased EFW Z-scores (β = -0.152, 95% CI: -0.230, -0.073) and higher risk of EFW undergrowth (RR = 1.651, 95% CI: 1.106, 2.464). Indoor air pollution and ambient PM2.5 exposure had a similar joint effect on the Z-scores and undergrowth parameters of fetal growth.

CONCLUSIONS

This study suggested that indoor air pollution and ambient PM exposure had individual and joint negative effects on fetal growth.