Reversible Movement of Fluid Across the Fœtal Lung

Abstract

IN 1953, attention was directed to the nasopharyngeal and buccal cavities as a source of amniotic fluid in fœtal lambs in the last trimester of gestation¹. Since that time, interest in the subject has continued. Dawes², Jost³, and Adams et al.⁴ have all directed attention to the fact that fluid is derived from the fœtal lung and moves up the trachea through the upper respiratory tract and thence, with mucus added, into the amniotic fluid. The view of Paul et al.⁵ is that, “diffusion is the mechanism of passage of water across the barrier between maternal blood and amniotic fluid and that the barrier provides a significant restriction to free diffusion”. Adams et al.⁴ hold that, “tracheal fluid is formed in the fœtal lung either as the result of ultrafiltration with selective reabsorption or ultra-filtration with selective secretion”.