[Fetal dysmorphology: a practical approach in utero].

Dysmorphology is the study of congenital malformations and anatomic variations of the individuals. Up to 2500 dysmorphic or malformative syndromes are described, most of them being characterized by mental retardation. Craniofacial dysmorphology may be the keystone of syndrome identification, although limb anomalies are sometimes important diagnostic clues. The advances of fetal imaging, particularly the development of 3D ultrasound techniques, allow a detailed analysis of the fetal face. Dysmorphology requires experience of rare syndromes and a perfect knowledge of normal facial appearance and variations. In utero, this approach must combine the skills of both a practitioner with expertise in fetal ultrasound and a pediatric dysmorphologist. Furthermore, facial changes have to be analyzed according to the context of the pregnancy and family history. Identification of patent facial anomalies may be a clue for the diagnosis of severe fetal syndromes and diseases. Conversely, when fetal malformations or abnomalities of the fetal growth are identified, a careful facial analysis can be proposed in order to rule out well-known syndromes with a poor prognosis. However, from an ethical point of view, parents should not be aware of a possible facial dysmorphism unless there is a precise diagnosis and options concerning the pregnancy.