This article is a critical analysis of a study published in the journal *Environmental Health Perspectives* 2004;112:1398-402. Numerous studies have demonstrated the relationship between, on the one hand, tobacco use, parental secondhand smoke, and exposure to air pollutants, and, on the other hand, the risk of preterm birth and intrauterine growth restriction. It is known that fetuses and children are more sensitive than adults to toxic substances present in the environment. Exposure to pollutants (e.g., PM10—particles with a diameter of 10 micrometers or less—CO, or SO2) is estimated in most of these studies based on ambient pollutant concentrations. These concentrations are measured using air quality monitoring sensors and are then attributed to the people living in those areas. These studies, particularly ecological studies, generally do not account for factors known to affect intrauterine growth (such as the mother’s height, weight, and tobacco use). The Polish study discussed here is unique because it uses self-reported exposure estimates and incorporates these various confounding factors into its analysis. The objective of the study is to investigate whether there is a relationship between pregnant women’s personal exposure to PM2.5 and the baby’s height, weight, and head circumference at birth. The results obtained reinforce those of numerous other epidemiological studies highlighting the effects of fine particulate matter on health at various levels (carcinogenicity, respiratory and cardiovascular conditions, etc.). From a broader perspective, this study provides further evidence of the public health imperative to better assess the health risks associated with exposure to fine particulate matter. However, as the authors note, further research is needed to understand the mechanisms by which these particles affect fetal development. The answer may come from more in-depth studies on the physicochemical nature of these so-called fine or even ultrafine particles.