The fetal Ear-Eye and Ear-Rotation angle: A pilot study on novel 3D ultrasound measure-ments for prenatal diagnosis of low-set ears.

INTRODUCTION

Low-set ears are frequently associated with chromosomal aberrations, congenital malformations, and genetic syndromes. While typically described postnatally, prenatal diagnosis usually relies on subjective expert pattern recognition. We introduce a standardized 3D ultra-sound measurement approach to assess fetal ear position relative to the eye and head.

METHODS

Retrospective pilot analysis of prospectively acquired 3D head volumes (16-34 weeks; 10/2023-10/2025). The "ear-eye angle," "ear-rotation angle," and ear length were meas-ured by two blinded examiners in healthy controls and a malformation group.

RESULTS

We included 102 fetuses (82 controls, 20 malformations) at a median 21 weeks' gesta-tion (16-34). The malformation group had a significantly larger median ear-eye angle than con-trols (3.29° [-2.81-7.88] vs. 1.02° [-11.04-8.75]; P<0.001) and median ear-rotation angle (17.50° [-33.75-37.20] vs. 12.10° [0.00-38.40]; P=0.029). Logistic regression showed that for every one-degree increase in the ear-eye angle, the odds of a malformation increased significant-ly (OR 1.36; 95% CI: 1.11-1.65; P = 0.002). ROC analysis revealed the ear-eye angle had supe-rior discriminative ability over the ear-rotation angle (AUC 0.76 vs. 0.66). Inter-observer agree-ment was high (ear-eye ICC=0.96; ear-rotation ICC=0.92).

CONCLUSION

Systematic evaluation of the fetal ear on routinely collected 3D volumes is feasible. Both angles were significantly larger in affected fetuses compared to healthy controls. However, due to the limited sample size and prevalence of abnormal cases, these diagnostic performance metrics should be interpreted with caution and require validation in larger cohorts.