A histological study of fetoscopic membrane defects to document membrane healing

Objective: To evaluate the rate of spontaneous healing in human fetal membranes after fetoscopy. Study design: Membranes from patients that had undergone fetoscopic interventions and delivered in one of the two treatment centers were included in the study. The membranes were examined macroscopically for any remaining defects and if present, the size of the defect in chorion and amnion was measured. Subsequently, the defect was excised and stained with HE for histological evaluation. Additional immunohistochemical staining was performed with Ki-67, cytokeratin and vimentin. The proliferation index (percentage of proliferating cells) was calculated in amnion and chorion. Results: Nineteen membrane defects were included in the study. The median time interval between invasive procedures and delivery was 60 days (range 3-112). All fetoscopic defects, (n = 19) could be identified in the gestational sac and in none spontaneous closure had occurred. Proliferation indices as measured by immunohistochemistry were very low (median 2.8%, range 0-7%) in the chorion and 0% in the amnion. Conclusion: No evidence of spontaneous membrane healing was found after fetoscopic procedures, suggesting that the membrane defect normally persists until delivery. Absence of amniotic fluid leakage after invasive procedures may be based on mechanisms other than histologic membrane repair.