ABSTRACT
Approximately 22% of twin pregnancies are monochorionic and about 10%–15% of monochorionic twin pregnancies are complicated by severe twin-to-twin transfusion syndrome (TTTS) as a result of a chronic circulatory imbalance in the vascular anastomoses that connect the fetuses. Chronic TTTS typically presents in the mid-second trimester with a host of maternal and perinatal findings. Chronic TTTS is diagnosed prenatally on the identification of the donor twin presenting with oligohydramnios or anhydramnios and the recipient twin simultaneously having polyhydramnios. The donor appears to be stuck with a lower estimated fetal weight and an absent or small fetal bladder. Attempts have been made to stage the process in TTTS; however, the relationship of this staging to the natural history and outcome of TTTS remains to be established. Laser photocoagulation involves the introduction of a laser fiber through a fetoscope into the recipient's sac under ultrasound guidance.
