Air pollution exposure during pregnancy and fetal markers of metabolic function: the MIREC Study.

Lavigne E, Ashley-Martin J, Dodds L, Arbuckle TE, Hystad P, Johnson M, Crouse DL, Ettinger AS, Shapiro GD, Fisher M, Morisset AS, Taback S, Bouchard MF, Sun L, Monnier P, Dallaire R, Fraser WD. American Journal of Epidemiology. 2016 2016 May 1;183(9):842-51. doi: 10.1093/aje/kwv256

A few laboratory animal studies have suggested that prenatal or early life exposure to air pollution may be associated with weight gain and obesity in children; however, studies in humans are scarce. One approach to examine this potential association is to measure the metabolic hormones leptin and adiponectin in umbilical cord blood. These two hormones may provide an indication of future child growth and obesity.

The MIREC Study recruited about 2,000 women between 2008 and 2011 from 10 cities across Canada. Approximately 1,300 mother-infant pairs were included in this analysis. The purpose of this study was to investigate the possible association between outdoor air pollutants (i.e., nitrogen dioxide and fine particulate matter) and infant levels of leptin and adiponectin. Each infant’s prenatal exposure to air pollution throughout the pregnancy was estimated from available data on air pollution in different geographic regions of Canada; the two hormones were measured in umbilical cord blood.

The study found that an increase in average outdoor exposure to fine particulate matter or nitrogen dioxide during pregnancy was associated with a small (11-13%) increase in adiponectin levels.

So far, no other study has examined this potential association, so it is unknown whether this association is real or occurred by chance. Following the MIREC children as they grow will provide more information on whether the hormone levels that were measured in cord blood are predictive of child growth and obesity and whether early life exposure to air pollution has a significant impact on child obesity.

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