Demonstration of Placental Vascular Anatomy in Monochorionic Twin Gestations

Abstract

Invasive treatment modalities for severe chronic twin-to-twin transfusion syndrome (TTTS), such as fetoscopic laser coagulation of communicating vessels, have revived the need for detailed studies of placental angioarchitecture. We describe a practical placental vascular injection technique using alcohol-resistant tissue-staining dyes. Injection of color-coded gelatin-dye mixtures effectively delineated the intertwin vasculature, and allowed unequivocal macroscopic classification of vascular communications as artery-to-artery, vein-to-vein, or deep artery-to-vein anastomoses. The existence of deep artery-to-vein anastomoses was further confirmed by light microscopic demonstration of venous dye of one twin and arterial dye of the opposite twin within the same stem villus. Furthermore, the injection technique allowed determination of the caliber of the anastomoses, the direction of the artery-to-vein anastomoses, and the relative vascular territory of each twin. Documenting the vascular communications in monochorionic twin placentas with and without TTTS may enhance our understanding of the pathogenesis of chronic TTTS. Correlating the anastomotic patterns and location of the laser coagulation scars with post-ablation outcome will aid in the design of rational therapeutic methods for this often lethal condition.

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“…Injection studies can be performed in fresh specimens to clarify the type of the anastomosis. 17 In fixed placentas, arteries may be identified by the fact that they are always superficial to the veins. Arterio-venous anastomosis (AVA) may be identified by the presence of an impaired vessel from one twin feeding an area drained by the co-twin.…”

Developmental genes targeted for epigenetic variation between twin-twin transfusion syndrome children

“…While survival of at least one twin is seen in 80% of cases [25], not all fetuses fully recover. In some, the renal, cardiovascular or neurological effects of the syndrome are already irreversible [26,27]; in addition, unequal placental share seen in some twin pregnancies (a problem that cannot be corrected by fetal surgery) causes persistent placental insufficiency and growth restriction, usually of the donor [28]. In part because of the inherent risks of twin gestations, the chronic morbidity of TTTS and the relative invasiveness of fetal intervention, TTTS pregnancies and infants may also suffer from miscarriage, preterm birth, neonatal intensive care unit admissions, respiratory distress syndrome and intraventricular hemorrhage [29].…”

Prevalence, Spectrum, and Outcome of Right Ventricular Outflow Tract Abnormalities in Twin-twin Transfusion Syndrome: A Large, Single-center Experience

“…1,2 The etiology of TTTS is unknown, but the presence of placental vascular anastomoses may allow intertwin transfer of vasoactive media-tors, with resultant polyhydramnios and hypertension in the "recipient" twin (RT) and oligohydramnios in the "donor" twin. [3][4][5][6] Cardiac changes in RT in TTTS have previously been reported and include ventricular hypertrophy, dysfunction, and atrioventricular valve regurgitation. 7-12 Right ventricular outflow tract (RVOT) abnormalities, such as pulmonary stenosis (PS) and pulmonary atresia (PA), have been 209…”