Multiple pregnancies and environmental exposure: An impact of air pollution on fetal growth?

Abstract

Introduction Multiple pregnancies display all the complications of singletons, but in highest frequencies, especially for fetal growth abnormalities. In singletons, air pollution seems to be negatively associated with fetal growth. A similar relationship in multiple pregnancies can be expected. However, multiple pregnancies are systematically excluded from the studies of the impact of air pollution on pregnancy outcomes. This study aims to analyze in a population of multiple pregnancies the relationship between fetal growth restriction (FGR), small for gestational age (SGA) and environmental chronic exposure to air pollution in moderately polluted cities. Methods All the multiple pregnancies of women living in the city of Besancon (121,671 inhabitants) or in the urban unit of Dijon (243,936 inhabitants) and who delivered in a university hospital between 2005 and 2009 were included. Births were classified as SGA if birth weight was Results This study included 249 multiple pregnancies and 506 newborns. Among the 249 pregnancies, 64 presented a FGR and 94 a SGA in one or more fetus of the pregnancy. The median of NO2 concentration within 50 m around building during entire pregnancy was 23.1 μg/m3 (minimum at 10.1 μg/m3 and maximum at 46.7 μg/m3). No association was observed between NO2 and SGA whatever the pregnancy period considered (the odds ratio (OR) for a 10 μg/m3 increase of NO2 exposure ranged between 0.78 and 0.88). Regarding FGR, the OR associated with a 10 μg/m3 increase of NO2 exposure during the first, the second and the third trimester were respectively 1.42 (95% confidence interval (CI = 0.97–2.08), 1.55 (95% CI = 1.06–2.27), 1.35 (95% CI = 0.92–1.98). The OR associated with a 10 μg/m3 increase of NO2 exposure during entire pregnancy and during the two last months before delivery were respectively 1.52 (95% CI = 1.02–2.26) and 1.53 (95% CI = 1.04–2.25). Sensitivity analyses with NO2 concentration in front of the residential building led to similar results. Conclusions In our study, environmental exposure to NO2 was associated with FGR in multiple pregnancies, especially during the 2nd trimester and the two last months before delivery. However, no association between NO2 exposure and SGA was identified. These results are in line with an impact of NO2 on fetal growth in multiple pregnancies for an exposure under the European legislation threshold.