The human placenta is unique among mammals. We lack understanding of its immune complex and the innate responses that prevent or enable vertical transmission. The COVID pandemic highlights this gap. Where previous coronavirus outbreaks were associated with adverse pregnancy outcomes, SARS-Cov-2 does not appear to pass the placenta and negatively impact fetal development. Interestingly, several groups have highlight SARS-Cov-2 infection of the human placenta with no transmission to the fetus. It is possible that placental innate immune responses can fight this infection and prevent or limit SARS-Cov-2 transmission. Characterizing the human placental immune system and molecular mechanisms of action may yield insight for combating emerging pathogens such as SARS-Cov-2 and preventing transmission of known teratogens such Zika virus A firm understanding of placental immunity is fundamental to the human placenta project and warrants further emphasis.