Despite the widespread use of prenatal care, the evidence for its effectiveness remains equivocal and its primary purpose and effects continue to be a subject of debate. To provide some perspective on why the effectiveness and organization of prenatal care continue to be debated, the authors (a) briefly review the history of the development of prenatal care in the US; (b) attempt to conceptually define prenatal care in terms of its utilization, content, and quality; and, (c) highlight some of the research controversies and challenges facing investigators and advocates who seek to establish the value of prenatal care. In addition, the authors recommend directions for future research to address persistent questions regarding the function, structure, and significance of prenatal care in improving US perinatal outcomes.