*6.1.3 Selective fetal reduction*

In addition to TTTS, other serious problem that can affect monochorionic twin pregnancies, includes severe intrauterine growth restriction, structural anomalies, twin anemia polycythemia sequence, and TRAP sequence, or a cardiac twinning. In some complicated monochorionic pregnancies, elective fetal reduction is recommended especially for high risk of hemodynamic compromise or intrauterine fetal death, aimed to prevent neurologic injury or demise to the co-twin. Fetal intra-cardiac potassium chloride injection is contraindicated in these pregnancies, because of risk of transmission between twins and selective termination must be performed with interruption of blood flow to the fetus. This interruption usually performed through ligation of the umbilical cord, fetoscopic laser coagulation, ultrasound-guided and bipolar cord coagulation. Selective fetal reduction was seriously indicated in complicated twin pregnancies what is TRAP sequence. In TRAP sequence, one twin is incompatible with life due to absent or rudimentary heart, as well as absence of other vital structures, as head (anencephaly). This twin usually has no placental blood supply, and it receives its blood supply directly through vascular connections from the second normal twin (acts as pump twin). Therefore, the normal twin will rapidly develop high-output heart failure, with more than 50% mortality rate. Selective fetal reduction aims to stop blood flow to incompatible with life twin, and save the life of normal (pump) twin. In the largest review from 12 fetal centers from the North American Fetal Therapy Network registry data, identified 98 patients who underwent percutaneous radio frequency ablation of a cardiac twin. In this series, the overall survival of the normal (pump) twin to 30 days was 80% [46–50].
