The Fetal Larynx and Pharynx: Structure and Development Described by 2D and 3D Ultrasound Examination

Abstract

Objectives: Define the structure and function of the fetal pharynx and larynx. We describe for the first time the various components of these anatomical sites by 3D multiplanar and render modes during the late 1st and 2nd trimesters. Understanding these structures’ normal anatomy and function may contribute to our evaluation of pathologies. Methods: Gravidae with singleton fetuses were enrolled. Transabdominal 3DUS scan of the fetal neck was acquired. The pharynx width and height, upper, middle, and lower larynx width, and larynx height were measured. We developed a new approach based on 5 spatial planes: posterior and anterior coronal planes and high, mid, and low axial planes. Multiplanar reconstruction (MPR) in post-processing allowed adjustment of the volume to obtain the coronal plane of the area. Color Doppler was used to show fluid motion in the target area. 2DUS was also applied. Results: 582 fetuses were examined during the late 1st and 2nd trimester of pregnancy. Components identified were the sphenoid bone, pterygoid processes, constrictor muscles, piriform sinus, uvula, epiglottis, aryepiglottic folds, arytenoid, cricoid, and thyroid cartilages, and the vocal cords. We defined the bilateral mode of movements of the constrictor muscles, aryepiglottic folds, and vocal folds, and bidirectional fluid jet flows through the larynx. Conclusions: The fetal larynx and pharynx can be visualized and measured with 3DUS in the late 1st and 2nd trimester. Knowledge of normal anatomy and biometry may prove useful in the evaluation of anatomic or functional pathologies involving the fetal upper respiratory tract.