How can we diagnose and manage twin–twin transfusion syndrome?

Severe mid-trimester twin–twin transfusion syndrome (TTS) complicates about 15% of monochorionic twin pregnancies. If left untreated, the mortality is 80–100%. The pathophysiological prerequisite for the onset of TTS is unequal blood flow via arteriovenous placental anastomoses from the so-called donor to the recipient twin. This can result in hypovolemia, hypotension and oligo- or anuria in the donor, and hypervolemia, hypertension, polyuria and finally heart failure in the recipient. Leading sonographic signs of TTS include severe oligo- or anhydramnios and a small or absent bladder filling in the donor in contrast to polyhydramnios with increased bladder filling in the recipient. Patients might present with clinical symptoms due to massive polyhydramnios. In severe mid-trimester TTS, fetoscopic laser occlusion of the anastomosing vessels on the placental surface under local anaesthesia plus subsequent amniodrainage is the most promising therapeutic option at present. In acute TTS after 26 weeks of gestation, amniodrainage is the therapy of choice. All patients suspected of this high-risk condition should be referred to a specialized fetal medicine centre.