Sonographic femur length to trunk cross area ratio: prediction of fetal outcome in 30 cases in which micromelia was suspected.

AIM: The purpose of the present study was to investigate the potential value of fetal routine sonographic biometry in evaluating micromelias. METHODS: Thirty fetuses had a presumptive diagnosis of micromelia from antepartum ultrasound examinations during the period between 1 April 1996 and 31 March 2005. The postnatal clinical features, final diagnoses and outcomes were examined to retrospectively compare these cases with biometric parameters obtained from routine antepartum ultrasound examinations. RESULTS: Final diagnoses included skeletal dysplasia (16), small-for-dates (SFD) infant without any abnormalities (seven), chromosomal abnormality (three), pyruvate dehydrogenase complex deficiency (one), Marden-Walker syndrome (one), and suspected Freeman-Sheldon syndrome (one). One turned out to be a healthy infant. All cases were divided on the basis of the final diagnoses into three groups: skeletal dysplasia (16 fetuses), SFD and healthy infant (eight fetuses) and others (six fetuses). The ratios of femur length (FL) to mean FL at a given gestational age (%FL) and of FL to biparietal diameter (FL/BPD) were significantly lower in the skeletal dysplasia group than those in the other groups. Moreover, in the skeletal dysplasia group, when the lethal cases were excluded, the ratio of FL to fetal trunk cross area (FL/FTA) was significantly lower than that in the other groups. CONCLUSIONS: FL/FTA appears to be a useful parameter to help differentiate fetuses with non-lethal skeletal dysplasia from anatomically normal fetuses either with constitutionally short limbs or with intrauterine growth restriction (IUGR).