Intrauterine growth retardation (IUGR) occurs in approximately 3 to 10% of singleton pregnancies, in 9.1% of all twins and 9.9% of monochorionic twins. IUGR in monochorionic twins typically affects only one of the fetuses (selective IUGR or SIUGR). Spontaneous demise of the SIUGR twin can occur, and may result in concomitant demise (up to 40% risk) or severe neurologic handicap (up to 30% risk) of the other twin. These complications result from exsanguination of the appropriately grown (AGA) twin into the demised SIUGR twin through placental vascular communications.