Concentrations of xenobiotic chemicals in the maternal-fetal unit

Exposure to a variety of toxic chemicals has been associated with adverse health outcomes. Presumably, the most vulnerable population for these adverse health outcomes are fetuses that are exposed to toxicants in utero. Fetuses have immature organ systems and often their detoxification enzymes or enzymatic processes are not fully developed when exposures occur. Many xenobiotic chemicals have been shown to pass through the placental barrier and into the fetal blood stream. These exposures have been associated with adverse birth outcomes, neurocognitive delays and adult onset disease. Exposures associated with interuterine growth retardation have been linked to a variety of adult onset diseases such as coronary artery disease and diabetes. In this article, we review a variety of chemicals that have been known to enter the fetal environment and their potential to affect both early childhood and subsequently adult health. We restrict our review to chemicals shown to be present in umbilical cord blood, amniotic fluid, or meconium, thus unequivocally demonstrating the chemicals have entered the fetal environment. In some instances where known health outcomes have occurred from these exposures, we note these and any caveats associated with the exposures.