EAR LENGTH - A POTENTIAL SONOGRAPHIC MARKER FOR DOWN-SYNDROME

OBJECTIVES. The purpose of this study was to determine if antenatal so nographic determination of fetal ear length is a useful screening meth od for identification of fetuses with Down syndrome. METHODS: Ear leng th measurements were recorded in 418 fetuses undergoing ultrasound sca nning between 20 and 28 weeks of gestation. Four trisomy 21 and six tr isomy 18 fetuses were identified by karyotyping. The relationship betw een ear length and gestational age in the normal population was determ ined by linear regression analysis. expected ear length = -6.000 + 1.0 75 gestational age. The ability of measured-to-expected ear length cut -off ratios to discriminate between affected and non-affected fetuses was assessed. RESULTS: The mean ear length and measured-to-expected ea r length ratios were significantly lower in the affected group as comp ared to the normal one. A measured-to-expected ear length ratio of les s than 0.8 was 75.0% sensitive and 98.8% specific in detecting Down sy ndrome fetuses, and resulted in an 8.5% positive predictive value in t he general population. CONCLUSIONS: This preliminary study suggests th at antenatal ear length measurements might be a promising sonographic screening method for the detection of Down syndrome in the second trim ester of pregnancy.