Colour Doppler energy insonation of placental vasculature in monochorionic twins: absent arterio‐arterial anastomoses in association with twin‐to‐twin transfusion syndrome

Abstract

Objective To determine in vivo whether monochorionic pregnancies complicated by twin-to-twin transfusion syndrome are associated with absence of haemodynamically-compensatory arterioarterial anastomoses.Design Forty monochorionic pregnancies were prospectively recruited for an ultrasonographic survey of the chorionic plate using colour Doppler energy. Arterio-arterial anastomoses were identified by their characteristic bidirectional interference pattern on spectral Doppler. Angioarchitecture was confirmed by postnatal injection study.Setting Fetal medicine tertiary referral centre in London. Main Outcome MeasuresPresence of arterio-arterial anastomoses, development of twin-to-twin transfusion syndrome, survival.Results Arterio-arterial anastomoses were detected by colour Doppler energy in 2 1 pregnancies (53%), and there were no false positives. An arterio-arterial anastomosis was more commonly found in unaffected (n = 28) compared to pregnancies affected by twin-to-twin transfusion syndrome (n = 12), both by colour Doppler energy [20/28 (71%) vs 1/12 (8%); A = 63%, 95% CI 400/1A6%;,] and by postnatal injection study [25/28 (89?4) vs 3/12 (25%); A = 64%, 95% CI 37%-91%]. In pregnancies in which no arterio-arterial anastomoses were detected, a diagnosis of twin-to-twin transfusion syndrome was made in 58%, and the perinatal loss rate was 40%, compared with one case of twin-to-twin transfusion syndrome (5%) (P C 0.001) and a loss rate of 12% (P = 0.005) in pregnancies in which an arterio-arterial anastomosis was detected.Conclusion Twin-to-twin transfusion syndrome is associated with an absence of functional arterioarterial anastomoses in vivo in monochorionic twin pregnancies. This contributes to our understanding of the pathophysiology of twin-to-twin transfusion syndrome and confirms ex vivo studies demonstrating that twin-to-twin transfusion syndrome is associated with a paucity of superficial anastomoses. Prospective studies are indicated to determine the utility of colour Doppler energy for arterio-arterial anastomoses in predicting risk in monochorionic pregnancies.

Late Onset of Discordant Growth in a Monochorionic Twin Pregnancy: Vascular Anastomoses Determine Fetal Growth Pattern and Not Placental Sharing

“…Discordant fetal growth can occur early or late, can be mild or severe, and may disappear spontaneously [2]. Usually, unidirectional arteriovenous (AV) connections without adequate compensation by superficial anastomoses cause severe TTTS [3,4]. Haemodynamic functional superficial arterio-arterial (AA) anastomoses either prevent the onset of TTTS or reduce its severity [4].…”

Influence of twin-twin transfusion syndrome on fetal cardiovascular structure and function: prospective case-control study of 136 monochorionic twin pregnancies

“…2 Unbalanced inter-twin transfusion secondary to unidirectional flow through deep arteriovenous anastomoses, with a paucity or absence of compensatory bidirectional superficial arterioarterial anastomoses, is thought to be the cause. 3 The diagnosis is made ultrasonographically, usually in the second trimester, by demonstrating the oligohydramnios/polyhydramnios sequence (where the deepest pool of amniotic fluid is less than 1 cm in the donor twin and more than 8 cm in the recipient). 4 The donor becomes oliguric and volume depleted, while the recipient becomes polyuric, volume overloaded, and may develop hydrops fetalis.…”

Time domain computational modelling of 1D arterial networks in monochorionic placentas

“…The clinical implications of the presence of artererio-arterial anastomoses in monochorionic placentas is that they have been found to protect against the development of twin-twin transfusion syndrome [2,3] in fetuses. In the few cases which develop twin-twin transfusion syndrome the fetuses with an arterio-arterial anastomosis present have a higher survival rate [15].…”

“…To write the system of equations (1) and (2) in the characteristic form, the chain rule is applied to the pressure-area relationship, equation (3) …”