Background. Recently, an association between adverse pregnancy outcome and air pollution was hypothesized in several papers. The aim of the present study is to evaluate the impact of particles with aerodynamic diameter < 10 mm (PM10) on the intrauterine growth retardation (IUGR) in two regions with the different level s of air pollution. Methods and Results. The study group includes all singleton full term births of European origin over a two-year period in the district of Teplice (n=1,943) and Prachatice (n=883). Information on reproductive and health history and lifestyle was obtained from maternal questionnaires and medical records. IUGR was chosen as the indicator of reproductive effects. The mean concentration of PM10 for each women in particular gestational month was calculated. Three concentration intervals were constructed (low <40 mg/m 3 ; medium 40-50 mg/m 3 ; high >50 mg/m 3 ). Relative risk of IUGR was estimated for particular month and pollutant level. Influence of the potential confounders (maternal age, height and pre-pregnancy weight, smoking, season and the year of study) was controlled using logistic regression models; adjusted odd’s ratio (AOR) was estimated. Relative risk of IUGR in Teplice District was increased for medium PM10 levels (AOR=1.62 CI: 1.07-2.46) (P<0.02) as well as for high levels in the first gestational month (2.64 CI: 1.48-4.71) (P<0.001). The same association was observed also in Prachatice District, though the PM10 did not achieve the „high“ levels (>50 mg/m 3 ). AOR for IUGR for mothers exposed in the 1st gestational month to medium PM10 levels was three times the risk of those exposed to low levels (3.50 CI: 1.82-6.81) (P<0.0003). No similar relationship was observed in any other gestational stage. Conclusions. Influence of particles or other associated air pollutants on fetal growth in early ge station is one of several possible explanations of these results. Timing of this effect in both different regions is compatible with a current hypothesis of IUGR etio-pathogenesis. Seasonal factors, one of the other possible explanations, is less probable. More investigation is required to evaluate a possible causal nature of the relationship observed.

        Key words: air pollution, PM10, reproductive effects, intrauterine growth retardation, fetal growth retardation,