HEI Research Report 189 describes a study by Dr. Zhengmin Qian conducted in Wuhan, the capital city of Hubei province in China. Wuhan experiences temperature extremes and generally has higher air pollution levels than those seen in the United States and Europe. Dr. Qian examined whether increased exposures to air pollutants (particulate matter, sulfur dioxide, nitrogen dioxide, carbon monoxide, and ozone) during vulnerable pregnancy periods were associated with increased rates of preterm birth, low birth weight, or intrauterine growth retardation, using both a cohort and nested case-control design.