Assessment of Placental Vascular Anastomoses and Villous Maturation Discordance: Associations with Birthweight Discordance in Monochorionic Diamniotic Twins

Monochorionic diamniotic (MCDA) twins share a single placenta in which chorionic plate vascular anastomoses and territory-specific histological differences may relate to intertwin growth balance. Nevertheless, few studies have assessed these features together at the gross examination stage. Fifty-nine MCDA twin placentas were reviewed retrospectively to determine if grossly visible anastomoses and within-pair villous maturation discordance were associated with birthweight discordance. The anastomoses were classified as artery-to-artery/vein-to-vein (AA/VV) or arteriovenous/venoaterial-type and the discordance was graded as minimal, mild, or severe by comparing the F1 and F2 territories. AA/VV anastomoses were identified in 36 cases (61.0%). The birthweight discordance was lower in cases with AA/VV anastomoses than in those without (5.15% [interquartile range, 3.40~8.75] vs. 20.30% [14.20~28.60]; P<0.001), and this difference persisted after adjustment for gestational age (B=−15.150; 95% CI, −19.833 to −10.467; P<0.001). Severe villous maturation discordance was more frequent in cases without AA/VV anastomoses (56.5% vs. 5.6%; P<0.001), and its grade correlated positively with birthweight discordance (Spearman’s ρ=0.616; P<0.001). MCDA placentas lacking grossly visible AA/VV anastomoses showed greater birthweight discordance and more severe maturation discordance. Evaluating vascular anastomoses may provide pathologic information relevant to postnatal neonatal risk assessment.