Obstetric ultrasound has become well integrated into management of pregnancy, labor, and delivery. An increasing number of nurse-midwives have expanded their roles to include the use of this technology. This article reviews the basic principles of ultrasound physics, the content of ultrasound examinations, and the performance of basic scans. The uses of limited scans for third-trimester antepartum assessment and intrapartum management are reviewed. Issues surrounding the use of obstetric ultrasound, including limited scans, routine ultrasound screening, and necessary education, are discussed. Information on incorporating the use of ultrasound procedures into nurse-midwifery practice is included.