Ultrasonographic diagnosis of second-trimester skeletal dysplasias: a prospective analysis in a high-risk population.

Sixteen pregnancies in 15 women at high genetic risk for having fetuses with skeletal dysplasias were examined by use of ultrasonography during the second trimester. In addition to the routine examination of fetal head and body, the fetal calvarium, spine, ribs, pelvis, and long bones were specifically evaluated for bone brightness, deformity, fractures, and inappropriate growth. It was determined that 11 of the 16 fetuses were normal and five were abnormal. At birth, all 11 ultrasonographically determined normal fetuses were normal, and at birth or elective termination of pregnancy the other five were abnormal. All abnormalities detected by ultrasonography in the affected fetuses were found at delivery, including decreased bone brightness, deformity of the head and long bones, and fractures and abnormal growth of the long bones. On the basis of this study, it is felt that ultrasonography is highly accurate for the diagnosis of many second-trimester skeletal dysplasias.