Perfusion fixation for placental morphologic investigation.
Fifty placentas were collected after vaginal delivery or cesarean section from normal and abnormal pregnancies and were fixed under different conditions of perfusion using a peristaltic roller pump. In each case a physiologic-heparin perfusate was used for less than 10 minutes, followed by a buffered solution of glutaraldehyde-formaldehyde. The best results were obtained with placentas from cesarean sections perfused immediately after delivery with a pressure maintained under 60 mm Hg. Placentas of this group were fixed within 30 minutes and electron microscopy demonstrated good preservation of cellular ultrastructure. Perfusion fixation could be performed up to 6 hours after delivery with satisfactory histologic results. In these cases, electron microscopy revealed ischemic changes 10 minutes after delivery and severe necrosis 1 hour after delivery. When the perfusion pressure was maintained over 60 mm Hg, diffuse damage of the villous morphology was observed. Histomorphometric analysis showed significant differences between terminal villi from nonperfused (immersed-fixed) placentas and perfused-fixed placentas. The mean barrier and trophoblastic thicknesses and the mean volume fraction of trophoblast were significantly (P less than .001) increased in the nonperfused group compared with the perfused group.