Role of adjunctive medical therapy in the fetoscopic surgical treatment of twin-twin transfusion syndrome.

The underlying etiology of twin-twin transfusion syndrome (TTTS) is unknown, but our growing understanding of the cardiovascular features of TTTS suggests this may be a disease that could respond to transplacental medical therapy. Adjunctive medical therapy in TTTS with the calcium channel blocker nifedipine has been shown to improve recipient survival while having no effect on the donor. There is no significant difference in recipient survival from postoperative day 5 to birth suggesting that the survival benefit is confined to the effects of nifedipine in the perioperative period. Also, there is no significant effect of nifedipine on gestational age at delivery suggesting the survival benefit was unrelated to the tocolytic effects of nifedipine and more likely a result of hemodynamic effects in the recipient twins' cardiovascular system during the perioperative period. TTTS remains poorly understood but there appears to be good evidence suggesting twin-twin hypertensive cardiomyopathy is a large component of the pathophysiology in recipient twins. The initial findings of nifedipine's effectiveness as a targeted medical therapy to address TTTS cardiomyopathy and improve survival of recipient twins opens the door for further research for adjunctive medical therapies in TTTS.