THE NORMAL ASPIRATION OF AMNIOTIC FLUID BY THE CONCEPTUS

Abstract

At first doubted, then attributed to abnormal stimulation and finally only recently confirmed, fetal breathing movements apparently do occur normally in utero. There is general agreement, however, that these movements are not expansive enough to clear the respiratory dead space. In the present study, ¹²⁵I-labeled human albumin, ⁵¹Cr-labeled rabbit erythrocytes and ⁸⁵Sr-labeled polystyrene microspheres 15 mμ in diameter were injected either singly or in combination into the amniotic fluid of rabbit fetuses near term. The injections were done via hysterotomy incisions under xylocaine spinal anesthesia. Three to 24 hours later, the fetuses were delivered by hysterotokotomy. All fetal organs were assayed for radioactivity, and where appropriate, sectioned for light microscopy. Each of the labeled materials was found regularly in the fetal lungs and gastrointestinal tract, the microspheres being visualized in alveolar ducts and alveoli and in the intestinal lumen. Radiolabeled albumin injected into the amniotic fluid of 3 human conceptuses at 13 to 15 weeks of gestation was also found in fetal lungs and gastrointestinal tract when delivered by therapeutic hysterotokotomy 5 hours later. Interestingly, the human fetus at 3 to 4 months of gestation swallows approximately half of the amniotic fluid volume per day. The data suggest a normal penetration of amniotic fluid into the pulmonary passages as far as the alveolar ducts and alveoli.

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