INMA: “Exposure to ambient air pollution during pregnancy and preterm birth”


A study of several INMA cohorts has found a relationship between ambient air pollution exposure during pregnancy and elevated risk of preterm birth(gestational age at delivery less than 37 weeks). Four INMA cohorts have been involved in this multicenter study: Asturias, Gipuzkoa, Sabadell and Valencia, in which a total of 2644 pregnant women participated from 2003 to 2008. A total of 2409 women were included for this study.

Preterm delivery is one the most important determinants of infant morbidity and mortality. In 2010, globally around 15 million babies were born prematurely (11.1{3effe4377b6f02be2524d084f7d03914ac32a2b62c0a056ca3444e58c1f10d0b} of all births). Preterm birth is considered responsible for one-third of neonatal deaths, and also causes other health consequences later in life, hence the importance of research about possible factors that cause it.

A wide range of risk factors have already been related with preterm birth, including maternal exposure to air pollution. However, there is yet no conclusive evidence about the latter. Moreover, certain contaminants, like benzene, have not been studied.

For this reason the present study assessed the relationship between two ambient air pollutants, nitrogen dioxide (NO2) and benzene, with preterm birth. One of the greatest advances in this study was using methods to improve air pollution exposure classification during pregnancy and its trimesters.

Preterm birth among the studied population was 4.7{3effe4377b6f02be2524d084f7d03914ac32a2b62c0a056ca3444e58c1f10d0b}, being the percentage higher in Valencia and AsturiasNO2 levels were higher in the more densely populated areas, Valencia and Sabadell, while benzene concentrations were higher in Asturias, a more industrial area, and Valencia. Significant associations were found between ambient air pollution and preterm birth in women spending more than 15 hours a day at home. The Second trimester appeared to be a more relevant period for exposure to NO2, while for benzene the most relevant was the third trimester.

The results obtained by this study and by previous others about the relationship between maternal exposure to ambient air pollution and preterm birth, encourage the implementation of policies to reduce air pollution levels. At the same time, future research should study the possible biological mechanisms for this association.


Reference: Estarlich M, Ballester F, Davdand P, Llop S, Esplugues A, Fernández-Somoano A, Lertxundi A, Guxens M, Basterrechea M, Tardón A, Sunyer J, Iñiguez C. Exposure to ambient air pollution during pregnancy and preterm birth: A Spanish multicenter birth cohort study. Environ Res. 2016 May;147:50-8.