Efficacy of Fetal Ear Length as a Prenatal Marker of Chromosomal Anomalies: A Prospective, Multicenter Cohort Study in a Southern European Population.

To develop a nomogram of fetal ear length (FEL) by gestational age in a healthy pregnant Southern European population and assess its potential as a prenatal ultrasound marker of chromosomal anomalies in this demographic. This prospective, multicenter cohort study included low-risk pregnancies from 11 + 2 to 34 + 6 gestational age. A nomogram was constructed based on gestational age for healthy fetuses with normal perinatal outcomes. Intraobserver and interobserver reliability were evaluated. To assess the efficacy of FEL as a marker of chromosomal anomalies, a multivariate logistic regression analysis was performed; sensitivity and specificity were calculated. A total of 1923 FEL measurements were obtained from 1331 singleton pregnancies. Using data from healthy fetuses, a nomogram was constructed through linear regression analysis. Measurement feasibility was excellent, with intra- and interobserver correlation coefficients of 0.996 (95% confidence interval [CI]: 0.995-0.997) and 0.998 (95% CI: 0.978-0.999), respectively. FEL achieved a sensitivity of 81.8% and a specificity of 49.8% in detecting chromosomal anomalies. Multivariate logistic regression indicated that FEL ≤ 5th percentile significantly increased the likelihood of detecting chromosomal anomalies (odds ratio = 3.11); although the wide 95% CI (1.92-10.7) suggests a cautious interpretation of this finding. While FEL demonstrates potential as a prenatal marker of chromosomal anomalies, its clinical utility remains limited due to moderate sensitivity and specificity. Further studies are warranted to refine its diagnostic value in routine screening practices.