Fetal imaging in the skeletal dysplasias: overview and experience.

The skeletal dysplasias (osteochondrodysplasias) comprise a heterogeneous group of disorders that are characterized by generalized abnormalities of skeletal growth and development. Of approximately 125 well-described skeletal dysplasias, about 50 are clinically apparent and identifiable at birth. The prevalence of these dysplasias in the newborn is quite frequent and has been estimated to be between 3-4.5 per 10,000, and the overall frequency of skeletal dysplasias among perinatal deaths to be about 9 per 1,000. Over the past 23 years we have acquired an enormous experience in the International Skeletal Dysplasia Registry with skeletal dysplasias diagnosable at birth or earlier. More and more cases referred to the registry over the past 2 years have been diagnosed as abnormal by ultrasound during the second trimester. The results of our evaluation of almost 400 fetuses and stillborn babies with reference to detailed prenatal history and postmortem evaluation including radiographs, chondro-osseous morphology and even some biochemical and molecular studies are presented. The most common disorders diagnosed were osteogenesis imperfecta (OI), thanatophoric dysplasia, campomelic dysplasia and achondrogenesis type II. Twenty-two types of neonatally diagnosable skeletal dysplasias are discussed together with potential fetal (second trimester) ultrasound findings, the number of fetal ultrasound cases referred to this registry, the number of total cases of that disorder sent to our registry, and the inheritance pattern of that skeletal dysplasia. This information should prove helpful in the evaluation of future cases ascertained by ultrasonography in the second trimester.