Obstetric ultrasound is a rapidly developing field which involves a variety of professional groups. Its multidisciplinary nature results in difficulties for practitioners in keeping up-to-date with the latest advances: the information they need has up to now been scattered in radiological, obstetric, and scientific sources. This volume is the first in an annual series which will assess areas of clinical importance and review recent developments. Practitioners are now obliged to understand much more than simply the mechanics of producing ultrasound images. The series therefore includes contributions from a range of relevant fields, including obstetrics, radiology and sonography, medical physics, genetics, and pathology. Relevant to all professionals involved in obstetric ultrasound, this series will provide a current assessment of an increasingly complex subject.