Exposure to air pollution during early and late pregnancy may curb the normal growth of the developing fetus, suggests research published ahead of print in the Journal of Epidemiology and Community Health. Pollutants from traffic may be particularly important, the research suggests. The authors base their findings on singleton births between 1999 and 2003 in the state of New Jersey, USA. During this period, 492,678 singleton babies were born in New Jersey.