Normal placentation is essential for the health and well-being of both the mother and fetus throughout pregnancy. In humans, defective placental development contributes to pregnancy complications such as preeclampsia, fetal growth restriction, and preterm birth. The etiology of these pregnancy disorders is poorly understood since they are thought to arise during the early stages of development which is difficult to study in humans due to ethical reasons. My studies highlighted the expression of ERVK11q23.3, an ERVK locus present in the human but not the rhesus genome, that is highly expressed in mononuclear trophoblasts and upregulated in human preterm compared to term placental tissue. I also provide evidence that altered placental expression of ERVK11q23.3 influences IFN antiviral response, which may contribute to preterm birth and other pregnancy complications in humans.