Color and Transmittance of Human Amniotic Membranes

Abstract

Evaluation of the color of amniotic fluid during amnioscopy is influenced among other factors by the color of the amniotic membranes at the forebag and their permeability to light. In order to assess this factor objectively we determined the color and the spectral transmittance of 94 human amniotic membranes. Prior to birth 26 forebags were marked under amnioscopic control at the presenting portion with a silver nitrate pencil in order to identify this area after birth exactly and enable the composition of the layers of the amniotic membrane at the time of marking to be determined. Of the 26 labelled membranes 15 consisted only of the amnion, i.e. the chorion had ruptured prematurely. 1. The amnion transmits light better than the chorion and with the standard illuminant G shows a mainly non-saturated yellowish color. 2. Amniotic membranes which contained discolored amniotic fluid did not demonstrate a decreased transmittance when compared to amniotic membranes with clear or milky amniotic fluid; however, they were slightly discolored. 3. Amniotic membranes from premature or at term deliveries are significantly more permeable to light than membranes from overdue placentas. This result may be explained in part by the increased thickness. 4. The transmittance to light is decreased in the amniotic membranes of mothers who had undergone amnioscopy more than five times. 5. The transmittance of the amniotic membrane is inversely proportional to its thickness. Measurements for thickness were done on histologie preparations which had been fixed in glutaraldehyde in order to minimize shrinking and/or swelling. 6. Spectrophotometric measurements of samples of amniotic fluid together with amniotic membranes demonstrated that the amnion did not have a significant influence on the color of the amniotic fluid. 7. The complete membrane influences the color of the amniotic fluid more definitely. Specifically membranes with a decreased transmittance may change the color characteristic of slightly discolored amniotic fluids.