Intratwin arteriovenous fistula of the placenta in a case of twin-to-twin transfusion syndrome.

Arteriovenous fistulas of the placenta are extremely rare in singleton pregnancies and, to our knowledge, have not previously been reported in twin gestations. We describe a case of an arteriovenous fistula of the placenta in a diamniotic-monochorionic twin pregnancy complicated by twin-to-twin transfusion syndrome (TTTS). The arteriovenous fistula was demonstrated by color-coded vascular injection studies of the placenta. We speculate that the hemodynamic effects of the fistula may have contributed to the refractoriness of the TTTS to serial amniodrainages and laser ablation of communicating intertwin vessels.