Formerly the policy of masterly inactivity was generally accepted in obstetrical practice. However, this is no longer true at the beginning of the present decade, and the authors are to be congratulated in trying to stimulate their juniors to approach the problems of Pre-natal Paediatrics in a well informed manner. Whilst inactivity may still be the treatment of choice in certain cases, it should only be carried out with the full knowledge that all is well, and this obviously will involve the use and understanding of new investigations and techniques. In my opinion the authors have achieved their aims and though there are those who may always have reservations, they must surely accept the authors' appraisal of the modern approach to this science. VICTOR R. TINDALL Cardiff, I97 I PREFACE This book confines itself to those aspects of pre-natal develop ment which are of importance to the clinician. We hope to present a reasonably concise account of this relatively new and rapidly expanding field of medical science. Stress is given to concepts which may not yet be in many standard obstetric and paediatric texts. Also, we wish to provide an easily accessible collection of reference data for the busy member of junior staff to refer to during the course of his routine work. We therefore make no apology for any repetition needed to make each section readable without many cross references.