Twin-twin transfusion syndrome: etiology, severity and rational management

The twin-twin transfusion syndrome is a serious complication of monochorion ic twin pregnancies. Partly as a result of an inadequate understanding of t he pathophysiology of the syndrome, there is a lack of consensus in clinica l management. We sought to review the available information on the etiology of twin-twin transfusion syndrome, to identify parameters that contribute to the severity of the syndrome, and propose a rational management plan bas ed on pathophysiology, clinical presentation and the efficacy of therapies. We therefore amalgamated recent advances in twin-twin transfusion syndrome computer modelling and clinical studies, particularly on therapeutic outco mes. We round that the oligo-polyhydramnios sequence that defines twin-twin transfusion syndrome prenatally represents a wide continuum of severity in the imbalance between the fetoplacental circulations of both twins. In sev ere twin-twin transfusion syndrome cases, in which the circulatory imbalanc e deteriorates beyond fetal control, fetoscopic laser therapy of all anasto moses along the placental vascular equator is predicted to have significant ly better survival rates and fewer neurological sequelae than amnioreductio n, In contrast, mild twin-twin transfusion syndrome cases have better outco mes after one or at most a few amnioreductions than laser therapy, as a res ult of significantly fewer procedure-related risks. In conclusion, optimal individual therapy may possibly achieve an 85% survival rate in twin-twin t ransfusion syndrome, but requires advancement in non-invasive criteria that predict the severity of the syndrome. identifying such criteria is a futur e challenge. For the interim, twin-twin transfusion syndrome diagnosed befo re 26 weeks' gestation has significantly better survival rates and fewer ne urological sequelae after laser therapy than amnioreduction, Twin-twin tran sfusion syndrome diagnosed after 26 weeks can best be treated by amnioreduc tion, or delivery. Contrary to previous claims, fetoscopic laser therapy ha s outgrown its experimental status. Although improvements in technique and technology are likely, laser placental ablation has a firm scientific and c linical basis. Curr Opin Obstet Gynecol 13:193-206. (C) 2001 Lippincott Wil liams & Wilkins.