Histological changes in the endometrium of women suffering from recurrent pregnancy loss: light and electron microscopic study

Recurrent Pregnancy Loss [RPL] is defined as the occurrence of three or more consecutive spontaneous abortions before 20 weeks gestation.In human, natural killer cells [NK] are present in abundance in the endometrial stroma and appear to play an important role in early pregnancy. This study was designed to investigate the histological changes which occurred in the human endometrium in women suffering from RPL compared to fertile controls. This study was performed on 20 non-pregnant healthy women. Fifteen of them had a history of three or more spontaneous consecutive first trimester abortions and represented as [RPL group]. Five women had at least one successful child birth and considered as control group. Endometrial biopsies were obtained and were processed for haematoxylin and eosin, immunohistochemical stain for CD 56, transmission and scanning electron microscopic study. Compared with control group, RPL group showed that some cells of epithelial lining revealed vacuolated cytoplasm with karyolytic nuclei and others revealed condensed apoptotic nuclei. The stroma showed apparent increase in the number of positive CD 56 specific for NK cells. Also, in semithin sections the stroma showed apparent increase in the lymphocytes like cells. By TEM, the secretory cells revealed degenerated mitochondria, distorted microvilli, and condensed apoptotic nuclei. The ciliated cells showed disorganization of their cilia, degenerated mitochondria and many cytoplasmic vacuoles. By SEM, the ciliated cells showed short, fused and disorganized cilia while some of the secretory cells appeared degenerated, shrunken and widely separated. No apical secretory cell projections [pinopodes] could be observed. It was concluded that the endometrium of RPL patients showed some histological changes concerning the surface epithelial lining associated with an apparent increased number of NK cells in the stroma. Further studies are needed to explore the role of NK cells in the occurrence of idiopathic RPL