Surface ultrastructure of amniotic fluid cells and fetal tissues of the Rhesus monkey.

Amniotic fluid cytology is considered to reflect other organ maturity more faithfully than the L/S ratio. In order to assess the origin of amniotic fluid cells a pilot study was undertaken in the Rhesus monkey with the purpose of correlating the surface ultrastructure of amniotic fluid cells and various tissues facing, or communicating with the amniotic cavity. Three distinct cell types were found in the amniotic fluid, out of which two were obviously related to maturational events in fetal skin. The remaining cell type seemed to be derived from umbilical cord, fetal vagina and to some extent oral mucosa. No exfoliation was observed in the urinary bladder, trachea, lungs or amniotic membranes. It is concluded that correlation of cytology and tissue surface morphology in the monkey amniotic fluid compartment may give clues to the origin of amniotic fluid cells in the human.