The pregnant host is at risk for any of the viral diseases her nonpregnant counterpart acquires. Additionally, pregnancy heightens our concerns regarding specific viral diseases be cause of their potential for enhanced adverse effects on both maternal and fetal well-being. All too often the obstetrician relinquishes responsibility for the management of the gravida infected by a viral pathogen, and those expert in infectious diseases are confounded by the influence of pregnancy on these conditions. A major goal of this textbook is to narrow the gap between the two aforementioned management dichotomies in the virally infected pregnant woman. Weare at the infancy of our understanding of viral infections in pregnancy. The current and anticipated advancements are due in large part to a burgeoning oftechnological achievements in the areas of immunodiagnostics, molecular biology, and pharmacotherapeutics. Our in utero diagnostic capabilities, both invasive and noninvasive, have also allowed us new opportunities to study the effects of various maternal infectious disease processes on the developing fetus. New insights have been recognized pertaining to the maternal-fetal interface, the placenta, in that this structure is now acknowledged to function as both a mechanical and an immunological barrier to vertical transmission of infection. These observations suggest that there will be an outpouring of new data in the next several years that clinicians will need to master to maintain an appropriate level of expertise in the care of their patients.