This textbook contains materials concerning the essentials of the modern organization of obstetric care in the Russian Federation. The volume I contains gene ral terms, principles and mother-and-child healthcare system, which are aimed at prevention of complications of pregnancy and labor, as well as postpartum period. The volume I of this textbook is devoted only to physiological obstetrics: regulation and functions of reproductive system, physiology of pregnancy according to trimesters, the current trend in clinical obstetrics, aspects of physiological labor and postpartum period, as well as early neonatal period. For students of the institutions of higher medical education, residents, postgraduate students, attendees of retraining courses, teachers, as well as general practitioners and obstetricians.