The associations of air pollution exposure during pregnancy with fetal growth and anthropometric measurements at birth: a systematic review and meta-analysis

Fetal growth has been demonstrated to be an important predictor of perinatal and postnatal health. Although the effects of maternal exposure to air pollution during pregnancy on fetal growth have been investigated using ultrasound in many previous studies, the results were inconsistent and disputable. We aimed to qualitatively and quantitatively investigate the associations of air pollution exposure during different periods of pregnancy with fetal growth and anthropometric measurements at birth. We searched for all studies investigating the associations of air pollution exposure during pregnancy with fetal growth and birth anthropometric measurements in English and Chinese databases published before July 31, 2017. A random-effects model was employed in the meta-analysis to estimate the pooled effects of each 10g/m(3) increment in air pollutant exposure. The ACROBAT-NRSI tool was applied to assess the quality of each included study, and the GRADE tool was employed to assess the overall quality of the meta-analysis. Maternal PM2.5 exposure (10g/m(3)) during the entire pregnancy was negatively associated with head circumference at birth (=-0.30cm, 95% CI -0.49, -0.10), and NO2 exposure during the entire pregnancy was significantly linked to shorter length at birth (=-0.03cm, 95% CI -0.05, -0.02). Maternal exposure to higher NO2 and PM2.5 during pregnancy may impair neonatal head circumference and length development, respectively. More studies are needed to confirm the effects of NO2 and PM2.5 and to identify the sources and major toxic components of PMs.