Fetal exposure to environmental chemicals; insights from placental perfusion studies

Introduction: The burden of environmental chemicals in the human population is ubiquitous and especially problematic in pregnancy due to potential exposure of the vulnerable fetus. According to the Developmental Origins of Health and Disease hypothesis, the fetal period is highly sensitive to exposure to environmental factors that will determine the development of diseases later in life. A range of environmental chemicals has been studied in the ex vivo placental perfusion model, which is a human model using the intact placenta directly after birth to study the placental transfer and metabolism of selected compounds. Methods: Here, we reviewed the existing knowledge on human placental perfusion of environmental chemicals in order to identify potential correlations between placental transfer and properties of chemicals and areas of future research needs. Results: We found 32 studies of the following groups of environmental chemicals: pesticides, persistent organic pollutants (POPs), plastics and byproducts, phyto/myco-estrogens and fungal toxins, byproducts from heating/curing food, combustion in traffic and industry, and metals. The studies showed highly distinct transfer rates from very fast transport to the fetal side to negligible transfer. Discussion: In general, a low molecular weight favors placental translocation, but placental translocation is dependent on other physicochemical properties of the substances, claiming the need for more standardized studies and proper quantitative structure-activity relationship (QSAR) analysis. Overall, we recommend using placental perfusion studies in the risk assessment of environmental toxicants, to determine the transfer, metabolism and toxic effects of this diverse class of substances, on the human term placenta.