Book excerpt: This second edition has been comprehensively updated to reflect current clinical practice and the latest technical developments, including pre-implantation genetic diagnosis, array CGH, QF-PCR, non-invasive prenatal diagnosis and next generation sequencing amongst others. The first section covers basic principles, while the second outlines the more common situations where obstetrics and gynaecology interact with medical genetics. The third section contains real-life clinical case scenarios which have been selected to represent typical problems and to highlight areas which, if mismanaged, could have serious medico-legal consequences. Together with its accompanying website (www.essentialmedgen.com), it provides an invaluable guide to the use and selection of useful online genetic resources. This book is essential reading for candidates preparing for the MRCOG postgraduate examination, and any health professionals requiring a clear understanding of medical genetics and its increasingly frequent uses in obstetrics and gynaecology, where incorrect genetic advice can have serious consequences.