ANTENATAL DIAGNOSIS OF SHORT-LIMB DWARFISM - SONOGRAPHIC APPROACH

Based on the findings in 12 patients with skeletal dysplasia diagnosed antenatally, the authors propose a tailored approach to the evaluatio n of foetuses with shortened long bones, depending on the time of disc overy, the degree of shortening and the associated findings. During th e second trimester, a very short femur [2 standard deviations (SD) - 5 mm and less] most probably corresponds to a bone dysplasia, although the differential diagnosis is mainly early intra-uterine growth retard ation, and the foetal skeleton should be surveyed completely in order to find supplementary features suggestive of dwarfism. Anomalies of lo ng bones in their shape, thickness or contour, or spinal ossification disorders or undermineralisation (best evaluated at the level of calva rial bones) are most helpful in determining the type of dysplasia. A s hort femur (between 2 SD and 2 SD - 4 mm) may indicate growth retardat ion, a chromosomal anomaly or dwarfism. Followup examinations are mand atory in order to differentiate between them. During the third trimest er a very short femur may indicate a bone dysplasia and the work-up sh ould be the same as in the second trimester. A short femur may corresp ond to dwarfism of late development, a growth-retarded foetus or const itutional shortness. Various ratios, especially that of the femur/foot , are helpful in differentiating between them. In case of previous fam ily history, a short or very short femur usually indicates recurrence of the dwarfism. In all cases of antenatal diagnosis, confirmation of the sonographic findings should be obtained either by foetal or neonat al radiographs. The approach proposed by the authors should provide su fficient information to counsel the family not only for the ongoing pr egnancy but also for subsequent ones.