Multiple pregnancies and air pollution in moderately polluted cities: Is there an association between air pollution and fetal growth?
Résumé
Background: Multiple pregnancies (where more than one fetus develops simultaneously in the womb) are systematically
excluded from 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 exposure to air pollution in moderately polluted cities.
Methods: All women with multiple pregnancies living in the city of Besançon or in the urban area of Dijon and
who delivered at a university hospital between 2005 and 2009 were included. FGR and SGA were obtained from
medical records. Outdoor residential nitrogen dioxide (NO2) exposure was assessed using the mother's address,
considering a 50m radius buffer over the following defined pregnancy periods: each trimester, entire pregnancy
and two months before delivery. Logistic regression analyses were performed.
Results: This study included 249 multiple pregnancies with 506 newborns. The median of NO2 concentration
considering a 50m radius buffer 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 (the
odds ratio (OR) range 0.78 to 0.88). Regarding FGR, the OR associated with an increase of 10 μg/m3 of NO2
exposure during entire pregnancy was 1.52 (95% Confidence Interval (CI): 1.02–2.26). Similar results were
observed for NO2 exposure during the various pregnancy periods.
Conclusions: These results are in line with an association between NO2 and fetal growth in multiple pregnancies
for an exposure mostly below the threshold set out in European legislation.