Prenatal sonographic diagnosis of skeletal dysplasias. A report of 47 cases.

The purpose of this study was to evaluate the foetal sonographic efficiency for prenatal diagnosis of osteochondrodysplasias. Forty-seven prenatal and postnatal cases diagnosed between January 1993 and December 1998 in the referral sonographic centres of Strasbourg were studied. All cases were reviewed retrospectively and the prenatal ultrasound findings and diagnosis were compared to the postnatal or post-mortem diagnosis. Each case was studied by ultrasonographers, geneticists, radiologists, and foetopathologists. Final diagnosis was based on clinical examination, skeletal survey and molecular testing as deemed necessary. Routine screening and dating was the indication for foetal sonography in 72% (32/47) of our cases. The most likely time of diagnosis was between 16 and 24 weeks of gestation (17 out of 47 cases, 36%), which corresponds to the time of foetal anomaly sonographic scan in France. The other cluster of cases (12 among 47, 26%) was disclosed before 16 weeks of gestation. These results illustrate the importance of a detailed evaluation of the limbs during sonographic examinations of first and second trimesters of pregnancy. While the identification of skeletal dysplasias was relatively easy in our study, the ability to make an accurate specific antenatal diagnosis was more difficult. An accurate diagnosis was proposed in 28 of the 47 cases (60%). In 19% of the cases (9/47), the prenatal diagnosis was not accurate; in 21% of the cases (10/47), the prenatal diagnosis was imprecise. In 45 of the 47 cases (96%) prenatal foetal scan correctly predicted the prognosis.