Swallowing in fetal sheep.

Swallowing was measured in fetal sheep by using electromagnetic flowmeter heads chronically implanted in the fetal esophagus. The fetus swallows 20 to 200 milliliters of amniotic fluid in two to seven discrete episodes per day. The episodes are 1 to 9 minutes in duration and occur at seemingly random intervals. Swallowing is influenced by the condition of the fetus and may be the first manifestation of eating and drinking behavior.