Timing of Histological Distal Villous Fetal Vascular Malperfusion in the Placenta: Clinical Significance and Placental Features.

Objective: This retrospective analysis compares the diagnostic value of placental large vessel (global, partial) and distal villous (complete, segmental) fetal vascular malperfusion (FVM), remote/established, recent and on-going.

Methods: 24 independent abnormal clinical and 46 placental phenotypes were retrospectively statistically analyzed among 1002 consecutive cases, mostly with congenital anomalies in which CD34 immunostaining was performed. Group A: 398 cases without distal FVM and none or up to two large vessels FVM lesions. Group B: 221 cases with distal villous FVM without clustered endothelial fragmentation by CD34 immunostain. Group C: 145 cases with clustered endothelial fragmentation by CD34 immunostain but no clustered sclerotic or mineralized distal villi. Group D: 163 cases with coexistence of distal villous lesions of Group B and Group C. Group E: 75 cases with three or four lesions of large vessel FVM, but no distal villous FVM lesions.

Results: Established and/or remote FVM had clinical/placental associations similar to those of recent FVM, but on-going FVM was most commonly high grade and associated with preterm pregnancies, stillbirth, and fetal growth restriction. Large vessel FVM usually occurs in advanced third trimester pregnancies with fetal congenital anomalies, villitis of unknown etiology, and intervillous thrombi but no direct association with abnormal fetal condition.

Conclusion: FVM was the most common pattern of placental injury in this material. Proximal FVM was more common than distal FVM, suggesting the sequence of occurrence and the likely umbilical cord compression etiology. CD34 immunostaining doubles the sensitivity of placental examination and frequently upgrades the FVM, making it an important adjunct to placental histology.