[Lethal osteogenesis imperfecta. Prenatal diagnosis].

INTRODUCTION: Osteogenesis imparfecta (OI) comprises a group of disorders principally affecting type I collagen, which result in increased bone fragility. Lethal forms are rare and are characterised by micromelia with malformation of the limbs. CASE REPORT: A prenatal diagnosis of lethal OI was made by ultrasonography at 18 weeks of gestation and therapeutic abortion was indicated. COMMENTS: Molecular biology and genetic studies offer new possibilities of prenatal diagnosis, but ultrasonography remains the investigation of choice. It confirms the diagnosis by revealing an increase in bone transparency.