Stereological Analysis of Human Placenta in Cases of Placenta Previa in Comparison with Normally Implanted Controls

Background: placenta previa (PP) is an obstetric complication that can affect maternal and fetal morbidity and mortality. Its prevalence is rising due to cesar-ean sections. There is no quantitative data of placenta in PP. In this study, quan-titative parameters of placenta in cases with PP in comparison with normally implanted controls were investigated. Methods: In this quasi experimental study, placentas from pregnancies with PP and normally implanted controls (n=10) were obtained from women who un-derwent cesarean section. Three full-thickness columns of each placenta were sampled using systematic uniform random sampling (SURS). Columns were cut into slices and slices were sectioned with 4 μm thickness. SURS selected sec-tions were stained by Masson’s trichrome. Stereological analysis was done on 8-10 SURS microscopic fields of each section. Absolute volume and volume den-sity of chorionic villi, inter-villous space, syncytiotrophoblast, fibrin and blood vessels in chorionic villi were estimated in both groups. Statistical analysis was done using Mann Whitney-U test and significant level was set at p<0.05. Results: There was a significant reduction in total volume and volume density of fibrin deposits on the surface of chorionic villi (p<0.05), and a significant increment in total volume and volume density of chorionic villous blood ves-sels in PP group in comparison with C group (p<0.05). Conclusion: Results showed that impairment in situation of implantation in PP can cause significant changes in the structure of placenta. These changes prob-ably can be influential on the evolution and survival of fetus.