Exposure to Wood Smoke Pollution During Pre-Gestational Period of Rat has Effects on Placenta Volume and Fetus Size

Studies in humans showed that prenatal exposure to urban air pollution (AP) influences fetal development, and increases the incidence of adverse pregnancy outcomes and some diseases in postnatal life. However, most of these were performed in environments where the main source of environmental particulate matters (PM) emission is diesel combustion by motor vehicles and industries, thereby ignoring the effects produced by wood smoke pollution. We hypothesized that morphological changes in the placenta could contribute to the reduction in fetal size associated with different periods of exposure to AP produced by wood smoke pollution prior to and during pregnancy. The objective of the study was to investigate the quantitative effects of long-term exposure to environmental levels of wood smoke pollution on the macroscopic and microscopic morphology of the placenta in rats. To test this, pregnant rats were exposed during pregestational and gestational periods to wood smoke pollution in indoor and outdoor environments. At 19 days of gestation, the placentas were obtained by caesarean and were prepared for histological, planimetric and stereological analysis. The volume and proportions of the placental compartments were estimated. In addition, stereological estimators in fetal capillaries were calculated in the labyrinth region. Crown rump length, fetus weight and litter weight were influenced by pregestational and gestational exposure periods. Exposure to wood smoke pollution during pregestational period has significant effect on the volume of the placenta, and consequently on fetal height. In conclusion, this study demonstrated that long-term outdoor exposure to wood smoke pollution from residential heating affects fetal health, decreasing the absolute volume of the entire placenta and the placental interface between the mother and fetus, decreasing the total volume of blood vessels present in the labyrinth region of the placenta and affecting the size of the fetus.