Résumé
Retrognathia with or without Pierre Robin's sequence are rare malformations of the face associating a facial dysmorphology and functional disorders. Theprenatal diagnosis remains difficult in spite of the development of the echography. The radiological cephalometry is the reference tool for the diagnosis of the facial dysmorphology and the study of the growth.To be applied in prenatal it must be adaptedto the echography and take into account the fetal growth of the face. Our study consisted in modelling the fetal growth of the three functional components of the craniofacial development: base of the skull, the midface and the nasal cavity, the mandible and the oral cavity.The anatomical part studied the maxillo-mandibular growth and relationship in the sagittal plan to 18 fetusesdistributed over the fetal period. The prechordal part of the base of the skull and the midface has a constant speedof growth while the vertical growth of the oral cavity accelerates at the end of the third quarter. The maxillo-mandibular overjet tend to increase and to reach7° at the end of third quarter. The main anatomical landmarks of the cephalometry are found onthe sagittal slide of the second quarter echography. The ultrasound maxillo-mandibular overjetwas 8° on average (n=52). From our data we propose a clinical study to validate the ultrasound fetal cephalometry and compare it with the postnatal functional data. We think that our functional model will allow to articulate better the various explanations of the facial growth and to understand the role of the function on the facial morphology.