title: Socioeconomic position and low birth weight among mothers exposed to traffic-related air pollution.
abstract: BACKGROUND
  Atmospheric pollution is a major public health concern. It can affect placental function and restricts fetal growth. However, scientific knowledge remains too limited to make inferences regarding causal associations between maternal exposure to air pollution and adverse effects on pregnancy. This study evaluated the association between low birth weight (LBW) and maternal exposure during pregnancy to traffic related air pollutants (TRAP) in São Paulo, Brazil.
  
  
  RESULTS
  Analysis included 5,772 cases of term-LBW (<2,500 g) and 5,814 controls matched by sex and month of birth selected from the birth registration system. Mothers' addresses were geocoded to estimate exposure according to 3 indicators: distance from home to heavy traffic roads, distance-weighted traffic density (DWTD) and levels of particulate matter ≤10 µg/m3 estimated through land use regression (LUR-PM10). Final models were evaluated using multiple logistic regression adjusting for birth, maternal and pregnancy characteristics. We found decreased odds in the risk of LBW associated with DWTD and LUR-PM10 in the highest quartiles of exposure with a significant linear trend of decrease in risk. The analysis with distance from heavy traffic roads was less consistent. It was also observed that mothers with higher education and neighborhood-level income were potentially more exposed to TRAP.
  
  
  CONCLUSIONS
  This study found an unexpected decreased risk of LBW associated with traffic related air pollution. Mothers with advantaged socioeconomic position (SEP) although residing in areas of higher vehicular traffic might not in fact be more expose to air pollution. It can also be that the protection against LBW arising from a better SEP is stronger than the effect of exposure to air pollution, and this exposure may not be sufficient to increase the risk of LBW for these mothers.
authors.affiliation: Department of Preventive Medicine, School of Medicine, University of São Paulo, São Paulo, Brazil.
authors.forename: Mateus
authors.initials: M
authors.lastname: Habermann
authors.affiliation: Department of Preventive Medicine, School of Medicine, University of São Paulo, São Paulo, Brazil.
authors.forename: Nelson
authors.initials: N
authors.lastname: Gouveia
mesh_terms: D000393:Air Pollutants / Q000009:adverse effects* / Q000032:analysis; D000397:Air Pollution / Q000009:adverse effects* / Q000032:analysis; D001938:Brazil; D016022:Case-Control Studies; D005260:Female; D006801:Humans; D007230:Infant, Low Birth Weight / Q000502:physiology; D007231:Infant, Newborn; D008297:Male; D018811:Maternal Exposure / Q000009:adverse effects*; D015999:Multivariate Analysis; D016017:Odds Ratio; D052638:Particulate Matter / Q000009:adverse effects / Q000032:analysis; D011247:Pregnancy; D012306:Risk; D012959:Socioeconomic Factors; D001335:Vehicle Emissions / Q000032:analysis
chemical_list: D000393:Air Pollutants; D052638:Particulate Matter; D001335:Vehicle Emissions