Exposures to engineered nanomaterials and ultra fine particulate air pollution are associated with early pregnancy loss or reduced fetal growth. Here we sought to evaluate whether exposure to nano-sized particles during pregnancy led to the generation of an exaggeratedly hypoxic environment within the utero-placental unit, contributing to the fetal growth restriction observed. These ex vivo and in vitro experiments identified two ways in which utero-placental hypoxia may be exaggerated with exposure; reduced perfusion through the utero-placental blood vessels and a hypoxic cellular response at the level of the cytotrophoblast layer of the placenta.