Twin-reversed arterial perfusion syndrome is a rare condition occurring in approximately one percent of monochorionic twin pregnancies, or twins that share one placenta.

One twin, usually structurally normal, is referred to as the “pump twin” because his/her heart is used to pump blood to the other twin. The other twin, called the “acardiac twin,” is abnormal, usually consisting of only legs and a lower body but no head, upper body or heart. It relies upon the normal twin for circulation, putting the pump fetus at risk of heart failure.

Because the normal pump twin’s heart must work extra hard and is at risk of heart failure. Left untreated, up to 50 percent of these otherwise normal twins die in utero or shortly after birth.


The condition is detected during routine ultrasound during pregnancy. Doppler imaging can detect the vascular abnormalities and confirm the diagnosis.


Treatment during pregnancy focuses on safely stopping flow to the acardiac mass so that the normal pump twin and his/her heart is protected. The most successful treatment involves a procedure called radiofrequency ablation. During this treatment, a surgeon uses real-time ultrasound guidance to place the ablation device through the mom’s abdomen and uterus and into the acardiac abdomen. Energy is deployed through the tip of the device to clot the vessels to the acardiac twin, stopping blood flow.

The major benefit of this technique is the extremely small size of the instrument used, typically leading to few or no complications for the mom.


The surviving twin will be completely evaluated at birth, especially for the health of his/her heart and brain. With prenatal treatment and term or near-term delivery, most do very well. All children with twin-reversed arterial perfusion syndrome should be born at a hospital with a team skilled with high-risk births and neonatal care.

The UC Davis Fetal Care and Treatment Center unites leaders in maternal-fetal care with renowned fetal, neonatal and pediatric surgeons to provide advanced diagnosis and treatment for complex conditions that can affect newborns. Often, the team can treat those conditions before birth at our advanced surgical facilities in Sacramento. Parents, parents-to-be and physicians who have questions about our services can contact us anytime by calling 916-794-BABY (2229) or emailing