CORRELATIONS OF PLACENTAL VASCULAR ANATOMY AND CLINICAL OUTCOMES IN 69 MONOCHORIONIC TWIN PREGNANCIES

Monochorionic monozygotic twins frequently suffer complications from t he presence of vascular anastomoses in their monochorionic placentas, Also, sharing of perfusion zones may be unequal, leading to marked gro wth discordance. This paper analyzes four measures of perinatal outcom e (gestational age at delivery, perinatal mortality, birth weight disc ordance, and presence/absence of hydramnios) according to the vascular patterns of the monochorionic placentas, The worst clinical outcomes were associated with arteriovenous anastomoses in the absence of arter io-arterial and veno-venous anastomoses. The vascular patterns of mono chorionic placentas cause significant fetal environmental differences within pairs of monochorionic monozygotic twins, These differences may cause life-long discordance for several phenotypic traits that are no t genetically based, and which cause monochorionic monozygotic twins t o be ''non-identical.'' (C) 1996 Wiley-Liss, Inc.