Exposure to air pollutants and risk of congenital anomalies: A systematic review and metaanalysis

Congenital malformations are considered as one of the significant causes of preterm as well as neonatal morbidity and mortality. Literature suggests the association of diverse congenital deformities with maternal exposure to air pollutants. However, the evidence is still inconclusive on the manifestation of these during pregnancy. Thus, systematic review was done on the available epidemiological studies studying the effect of air pollutants on congenital malformations. Furthermore, the meta-analysis was conducted for several combinations of air pollutants and congenital defects. Twenty six epidemiological studies were extracted from the databases and examined for association of risk of congenital defects with air pollutant concentrations. Metaanalysis was done if the risk estimates of the same anomaly and pollutant group were reported in at least three studies. Each study reported a statistically significant increased risk of congenital malformation with some air pollutant, amid the several tested combinations. Our meta-analysis reported that nitrogen dioxide and PM2.5 were associated with the risk of pulmonary valve stenosis with OR = 1.74 and OR = 1.42 respectively. The risk of developing tetralogy of Fallot (TOF) was observed to be associated with PM2.5 with OR = 1.52. SO2 exposure was related to a high risk of the ventricular septal defect (VSD) with OR = 1.15 and orofacial defects (OR = 1.27). It is evidenced that ambient air pollutants have some effect on congenital malformations. Standard case definitions, improved methods of exposure, and better control of confounders will improve future research in this area.