Abstract For more than a decade the importance of the microbiome and its role in health and disease has been appreciated, yet the virome (the viral component of the microbiome) has remained understudied. Physiologic changes during pregnancy and the postpartum period (often overlooked periods of the lifespan) include dramatic adaptations in immune response that provide a unique opportunity to study and understand the dynamic interplay between the virome and host. Both systemic and local modifications in innate and adaptive immunity have been described, characterizing an “immunological clock” of pregnancy. These programmed changes in immune response are critical for pregnancy success, providing a balance between fetal tolerance and effective protection from pathogens, including viruses. Individual viruses that cause adverse pregnancy outcomes have been frequently studied, for example those that cause more severe infection during pregnancy and those that cause congenital infections. However, the complex communities of the virome (in this case defined as all the viruses that infect human cells) have largely remained unexplored. We hypothesize that the dynamic, programmed changes in immune response through pregnancy and postpartum will alter the interactions between virome and host, revealing important underlying biology of the virome-maternal-fetal unit. To test this hypothesis, we will prospectively collect longitudinal samples from the pregnancy, delivery, and postpartum periods in a racially diverse cohort of 100 subjects enrolled at two sites to monitor the virome in tandem with local and systemic immune responses.