The main aim of this book is to help obstetricians and gynecologists recognize prenatal skeletal anomalies. Bone dysplasias alone represent about a third of all fetal malformations, some of which have different prognoses ranging from mild disabilities to severe or lethal ones. However, recognizing them prenatally is often difficult or impossible as they usually become apparent in the third trimester or even after birth. The majority of skeletal syndromes are extremely rare, making genetic testing necessary. The book is divided into sections, starting from the skull and ending with the feet, with each chapter discussing anomalies specific to that organ or bone deformation. It's a lengthy journey of 56 chapters that requires a precise and rigorous educational path to diagnose such diseases. However, by following the "Ariadne's thread" represented by the "characteristic sign" and the help of a geneticist, the difficult task becomes feasible.