Antenatal detection of skeletal dysplasias.

OBJECTIVE: To assess the accuracy of the prenatal diagnosis of skeletal dysplasias.

METHODS: All antenatally detected anomalies are coded in our ultrasound database, which is linked with a genetics database that includes outcomes. A final diagnosis is sought on the basis of radiographic studies, molecular testing, or both. Our ultrasound and genetics databases were queried for "skeletal dysplasias." All cases were reviewed specifically for the degree of bone shortening and other distinguishing characteristics on antenatal sonography.

RESULTS: Thirty-seven cases of skeletal dysplasia were antenatally diagnosed over an 8-year period. Complete follow-up was available in 31 cases. The mean gestational age at diagnosis was 22.7 weeks (range, 14-32.3 weeks). Twenty-one cases were diagnosed before 24 weeks. A final diagnosis was obtained in 80% of cases. The antenatal diagnosis was correct in 20 (65%) of 31 cases. There were 2 false-positive diagnoses. Specific final diagnoses included thanatophoric dysplasia (8), osteogenesis imperfecta (6), Roberts syndrome (2), achondroplasia (3), Ellis-van Creveld syndrome (1), metaphyseal dysplasia (1), spondyloepiphyseal dysplasia (1), distal arthrogryposis (1), caudal regression (1), and glycogen storage disorder (1). The condition was correctly thought to be lethal in 16 of the fetuses on the basis of early severe long bone shortening (13), femur length-abdominal circumference ratio of less than 0.16 (12), hypoplastic thorax (10), marked bowing or fractures (4), short ribs (4), caudal regression (1), and cloverleaf skull (1). The ability to predict lethality was 100%. There were no false-positive findings with respect to lethality.

CONCLUSIONS: Accurate antenatal diagnosis of skeletal dysplasias is problematic; in this series, only 20 of 31 cases were correctly diagnosed. However, the antenatal prediction of lethality was highly accurate. The most common predictors of lethal skeletal dysplasias included early and severe shortening of the long bones, femur length-abdominal circumference ratio of less than 0.16, hypoplastic thorax, and certain distinguishing characteristics.