[Echographic screening: small, yes... but why?].

This study concerns a case of micromelus dwarfism discovered after 30 weeks of amenorrhea, during a second systematic sonography performed in a second pregnancy without pathological history and a normal first pregnancy. This dwarfism is complete, without any associated malformations, but on the contrary a moderate hypotrophy. In addition, the morphology of the long bones is normal, without any evidence of fracture; hand and feet are in normal position, with five digits. Radiography of the uterine contents confirms these findings and shows a normal bony transparency. The karyotype is female, without any anomaly. Spontaneous delivery occurs normally at 39 weeks of amenorrhea. The little baby girl presents, at birth, a slight facial dysmorphism, low height and weight, without any other obvious malformation. The radiological and sonographic evaluation performed in the pre and postnatal periods does not permit a definite diagnosis. The diagnosis of achondroplasia or hypochondroplasia is temporarily made. At the age of 6 months, Laurie consults Professor Maroteaux, specialist in children bone diseases, who feels that this is more likely a congenital spondyloepiphyseal dysplasia. These extremely rare and unclear diseases make a precise prenatal diagnosis particularly difficult. A tentative classification according to the bony transparency and certain sonographic aspects, is presented at the end of this study, knowing that a diagnosis and therefore a prognosis should be considered with the utmost caution.