Low-Set Ears: A New Marker of Fetal Chromosomal Anomalies

Introduction: The aim of this study was to assess the clinical utility of low-set ears (LSE) as a novel 2D-ultrasound marker for the prenatal detection of chromosomal anomalies.

A multicenter cohort study including 1,331 singleton pregnancies between 11+2 and 34+6 weeks of gestation was conducted in the two participating centers to determine the performance of LSE as an aneuploidy marker. LSE was defined as a dichotomous marker using a newly defined axial plane of the fetal head in 2D ultrasound. Intra- and interobserver variability were assessed to ensure marker reliability. Efficacy in predicting chromosomal anomalies was assessed using LSE alone or in combination with aneuploidy screening.

A new axial plane of the fetal head, defined by both lenses and the cerebellum, was adopted for LSE detection. Intra-observer concordance Kappa index for LSE measurement was 1.0, and 0.82 for interobserver reliability. LSE could be assessed in 99% of the studied fetuses and was detected in 30 (2.3%) fetuses: in 19 (86%) of the 22 fetuses with chromosomal anomalies, in all cases (5/5, 100%) with other genetic anomalies, and in six (18%) of the 34 malformed fetuses without a genetic disorder. In one (3.3%) of the fetuses, LSE was not confirmed postnatally while the remaining 29 fetuses had an adverse outcome. When LSE was combined with aneuploidy screening, the detection rate of chromosomal anomalies remained the same and specificity increased from 89% to 100%.

Our study supports using LSE as a potential 2D-ultrasound marker for chromosomal anomaly detection. Studies with a larger sample size and in high-risk populations are warranted to prove its clinical utility before this marker can be included in prenatal screening protocols.