Objectives To examine the relationship between prenatal nitrogen dioxide (NO2) exposure and foetal growth in a prospective cohort of 1001 Chinese women.
Methods The maternal NO2 exposure levels were estimated using land-use regression models based on home address. The biparietal diameter (BPD), head circumference (HC), abdominal circumference (AC), femur length (FL) and estimated foetal weight (EFW) were evaluated via ultrasonography. The multiple linear regression model was used to adjust for confounders, and the mixed-effect model was used to assess longitudinal effect.
Results With a 10 μg/m3 increase in NO2 exposure, the BPD, HC, AC, FL and EFW in the second trimester decreased by 0.40 mm (95% CI −0.56 to −0.24), 1.07 mm (95% CI −1.60 to −0.54), 1.02 mm (95% CI −1.57 to −0.48), 0.24 mm (95% CI −0.37 to −0.12) and 7.84 g (95% CI −11.59 to −4.08), respectively; the BPD and HC in the third trimester decreased by 0.26 mm (95% CI −0.50 to −0.02) and 0.71 mm (95% CI −1.37 to −0.06), respectively. The longitudinal analyses showed inverse associations of NO2 exposure with BPD, HC, AC and FL (all p<0.05). The stratified analyses showed that the effects of NO2 on the HC, FL and EFW in the second trimester were stronger among female babies and that the effect of NO2 on EFW in the third trimester was stronger among smoking mothers (all p<0.05).
Conclusions In this prospective study of Chinese women, maternal NO2 exposure was inversely associated with foetal growth, and the association was stronger among female babies and smoking mothers.
- nitrogen dioxide
- fetal growth
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NY and SW contributed equally.
Contributors WW, SW and NY participated in conception and study design. WW and SW collected data for NO2 exposure estimation; WW, CZ, XZ, RC, XL, JW, LH, TX, CL and MX collected other data. SW, XY, LHao and NY supervised the study conduct. WW and SW contributed to the statistical analysis and wrote the manuscript. All authors have read and approved the final version of the manuscript.
Funding This work was supported by the National Program on Basic Research Project of China (NO.2013FY114200) for Nianhong Yang, the National Natural Science Foundation of China (NSF81172754) for Sheng Wei.
Competing interests None declared.
Ethics approval The Ethics Review Committee of Tongji Medical College, Huazhong University of Science and Technology.
Provenance and peer review Not commissioned; externally peer reviewed.