CD34 immunostain increases the sensitivity of placental examination for distal fetal vascular malperfusion in liveborn infants

Placental fetal vascular malperfusion (FVM) is associated with increased perinatal morbidity and mortality. This retrospective observational analysis was performed to compare the impact of large proximal vessel (global) FVM, established/remote distal villous FVM, and recent (acute) FVM diagnosed by clustered endothelial fragmentation by CD34 immunostaining, on clinical and other placental phenotypes. Clinical and placental phenotypes of 581 consecutive high-risk pregnancies with a live birth divided in five groups based on presence and type of FVM were analyzed. CD34 immunostaining was performed on all cases to refine the diagnosis of FVM. The statistical analysis was by ANOVA and Chi square. FVM was present in 88% of placentas from pregnancies dominated by congenital anomalies. 43% of those had global FVM (partial, large proximal vessel) without distal villous changes, either acute (endothelial fragmentation) or established (avascular villi). Acute distal villous FVM without avascular villi did not link with significant perinatal morbidity/mortality, likely because of its short duration. Established distal villous FVM with active endothelial fragmentation, labelled as FVM with temporal heterogeneity, is associated with preterm births, preeclampsia, abnormal Dopplers, fetal growth restriction, highest cesarean section rate, and high grade FVM, particularly the latter. Lesions of global FVM are common, featuring relatively low sensitivity for perinatal complications. Caution is indicated in assigning significance to isolated lesions such as fetal vascular ectasia, intramural fibrin deposition and stem vessel obliteration. Established and on-going FVM diagnosed by using CD34 immunostain, is much more significant and portends the most complicated perinatal outcomes. •Fetal vascular malperfusion is the most common type of placental injury.•Large vessel FVM is more common on H&E slides than distal villous FVM.•Finding endothelial clustering by CD34 helps to identify high-grade FVM.