Studies on the ultrastructure of the term amnion in pathological pregnancy.

The ultrastructure of the amniotic epithelium at term was examined in cases of intrauterine growth retardation of the fetus and compared with amnions obtained from women with a clinically unremarkable pregnancy. In uterine growth retardation the amniotic cells exhibit a general deficiency of a series of functionally significant cell organelles. The RER is insufficiently developed, there is a diminution of the normally numerous free ribosomes as well as of those cell organelles which are involved in secretory function. A further atypical finding is the common lack of intercellular canals playing an important role in the transamniotic exchange of material. Besides this, a very poor development or a complete disintegration of the microfilamentous cytoskelet is generally noticed. The present findings give once again evidence for a very close relation between the structural appearance of the intercellular diffusion canals and the microfilamentous system. The results presented are suggestive of an amnion which is in a state of reduced secretory activity, additionally, due to the common lack of intercellular canals an inhibition of the interepithelial passage between the maternal and amniotic compartment cannot be excluded.