Pathophysiology of twin to twin transfuzion syndrome

Abstract

Twin-twin transfusion syndrome (TTTTS) is a pathological condition whereby a donor fetus bleeds into the circulation of a recipient fetus through the abnormal inter-twin placental anastomoses. The donor twin becomes anemic, hypovolemic, growth restricted, and as a consequence has a reduced urinary production. Since swallowing of the fluid is not impaired, the amniotic fluid volume progressively decreases. The recipient twin becomes hypervolemic. Lacking a mechanism to remove blood, the recipient twin eliminates as much fluid as possible, thus becoming hypercytemic or even hydropic in the more severe cases. The elevated urinary production from the recipient twin leads to polyhydramnios and an overdistension of the amniotic cavity, that compresses the donor and it's vascular supply against the uterine wall, further decreasing perfusion to the donor fetus. The reduction in amniotic fluid on the donor side results in a close apposition of the inter-twin membrane that fixes the donor fetus to the uterus, a condition nicknamed 'stuck twin'.

Keywords

• pregnancy
• twins
• zygosity
• chorionicity
• placental disorders
• ultrasound
• twin to twin transfusion syndroma
• fetal cardiac disorders
• associated syndromes