 prior studies reported an association between ambient air concentrations of total suspended particles and so2 during pregnancy and adverse pregnancy outcomes . 
 we examined the possible impact of particulate matter up to 10 microm ( pm10 ) and up to 2.5 microm ( pm2 . 
 5 ) in size on intrauterine growth retardation ( iugr ) risk in a highly polluted area of northern bohemia ( teplice district ) . 
 the study group includes all singleton full - term births of european origin over a 2-year period in the teplice district . 
 information on reproductive history , health , and lifestyle was obtained from maternal questionnaires . 
 the mean concentrations of pollutants for each month of gestation were calculated using continuous monitoring data . 
 three intervals ( low , medium , and high ) were constructed for each pollutant ( tertiles ) . 
 odds ratios ( ors ) for iugr for pm10 and pm2.5 levels were generated using logistic regression for each month of gestation after adjustment for potential confounding factors . adjusted 
 ors for iugr related to ambient pm10 levels in the first gestational month increased along the concentration intervals : medium 1.62 [ 95% confidence interval ( ci ) , 1.07 - 2.46 ] , high 2.64 ( ci , 1.48 - 4.71 ) . 
 ors for pm2.5 were 1.26 ( ci , 0.81 - 1.95 ) and 2.11 ( ci , 1 . 
 20 - 3.70 ) , respectively . 
 no other associations of iugr risk with particulate matter were found . 
 influence of particles or other associated air pollutants on fetal growth in early gestation is one of several possible explanations of these results . 
 timing of this effect is compatible with a current hypothesis of iugr pathogenesis . 
 seasonal factors , one of the other possible explanations , is less probable . 
 more investigation is required to examine these findings and alternative explanations.imagesfigure 1 
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