Perinatal medicine, which is concerned with the problems of the fetus and newborn, has rapidly developed in the last two decades as an important and challenging specialty. Rapid advances in the field, coupled with tech nological advances, now are making survival of infants with weights as low as 500 grams possible. Ventilator care for severe respiratory problems is on the verge of being replaced by surfactant replacement therapy; on the other hand, development of such technologies as extracorporeal mem brane oxygenation and jet ventilation has revolutionized the care of these sick infants. The advances taking place today in the field of perinatal medicine make periodic updates, like the one provided by this volume, a virtual necessity for clinicians and paramedical personnel alike. A distinguished group of specialists in various aspects of perinatal medicine has contributed to this book. Their wide-ranging experience and points of view should make this book a valuable reference for all physicians and allied health personnel involved in the care of the high-risk fetus and newborn. MANOHAR RATHI, M.D. Acknowledgements. I am grateful to the contributors for their cooperation in preparing the manuscripts, to my associates for their help and support, and to the publishers for their continued interest in this work. Above all, I thank Ms. Rose Aiello-Lech and Ms. MaryAnn Cichowski for their hard work in making this publication possible.