Fetal yawning activity in normal and high-risk fetuses: a preliminary observation

Objective To study yawning activity in healthy fetuses and in fetuses at hi gh risk. Methods Yawning activity was studied in 16 healthy and 22 high-risk fetuses . Studies were performed in the postprandial state at 09.00 and 12.00 in a quiet room with the woman in the lateral recumbent position. All ultrasound examinations were performed using a 3.5-MHz Acuson 128 PX curvilinear prob e. Fetal lips, mouth, tongue, pharynx, larynx, trachea and esophagus were s urveyed in serial coronal and sagittal planes. All fetal mouthing movements were analyzed by a review of the videotape in slow motion. Results In both normal and high-risk fetuses, yawning was represented by is olated mouthing movements and consisted of slow opening of the mouth with s imultaneous downward movements of the tongue. This phase occupied 50-75% of the yawning cycle. After reaching its maximum opening, the mouth remained wide open for 2-8 s and returned to its resting position within seconds. Gr owth-restricted fetuses demonstrated yawning patterns consisting of isolate d yawns similar to those seen in healthy fetuses. Unusual bursts of fetal y awning activity were recorded in anemic fetuses. Conclusion Yawning activity in anemic fetuses may represent a compensatory process to increase venous return to the heart.