Fetal pharyngeal distention--is it a normal component of fetal swallowing?

Fetal swallowing is one of the main mechanisms of amniotic fluid circulation. Swallowing mechanisms were studied in 34 healthy fetuses using modern ultrasound technology. The fetal lips and mouth, as well as tongue, pharynx, larynx, trachea and esophagus were surveyed in serial sagittal planes. Fetal swallowing movements were recorded and subsequently analyzed from the videotapes. All neonates were born at term in a satisfactory condition. Twenty-nine infants were breastfed, and five were bottle fed. No feeding problems were reported in these neonates. In 85% of fetuses, swallowing activity started with suckling movements followed by wide opening of the mouth. Next, low frequency tongue movements propelled the fluid bolus into the hypopharynx. In 15% of fetuses, this activity was associated with prolonged pharyngeal dilatation. Prolonged pharyngeal dilatation does not signify fetal neurological compromise as judged by good neonatal outcome and probably represents a normal variant of fetal swallowing.