Copyright © 2020 American Chemical Society. Elevated blood sera concentrations of perfluorinated and polyfluorinated alkyl substances (PFAS) are associated with many adverse human health effects, including lower birth weight children. Yet the biodistribution of PFAS between mother and fetus remains unknown. The first comparative uptake and in vivo biodistribution study of "long-chain"and "short-chain"PFAS was performed on healthy, pregnant mice via two routes of administration, tail vein injection and oral gavage ingestion. Two 18F radiolabeled PFAS, [18F]PFOA (C8) and [18F]PFHxA (C6), were administered to pregnant mice, and real-time distribution was investigated by dynamic positron emission tomography (PET). Post imaging, the biodistribution of the radiolabeled PFAS compounds were quantified by ex vivo gamma counting. Imaging following tail vein administration showed rapid uptake of both [18F]PFAS in placentae followed by transport into fetuses. Oral gavage showed a slower uptake but still exhibited transport across the placenta. PFAS uptake was found in all tissues examined, with the highest uptake being exhibited in the blood for both [18F]C8 and [18F]C6 via tail vein and the lungs via oral gavage. These initial results provide insight into the link between PFAS exposure in pregnant mammals and offspring health.