Twin reversed arterial perfusion (TRAP) is a rare condition affecting about 1% of identical twin pregnancies, also known as monochorionic pregnancies. In TRAP, the twins share a placenta but have separate amniotic sacs. The amniotic sac is a fluid filled membrane that surrounds and protects a developing fetus. In pregnancies with TRAP, one of the twins has severe abnormalities that are not compatible with life. Often, this twin is missing a heart or a head. The abnormal twin receives all of its blood from the other twin, which forces the healthy twin’s heart to work extra hard because it is supplying blood to both of them. This condition is dangerous because it places the otherwise healthy twin’s heart at risk for failure. The pregnancy is also at a higher risk for premature delivery.
TRAP can be detected during pregnancy using ultrasound. The pregnancy should be closely monitored after diagnosis. In some cases, most often when the abnormal twin in smaller than the normal twin, treatment is not needed. If the normal twin is at risk, procedures that cut off blood flow to the abnormal twin can be performed. If you have a pregnancy with twin reversed arterial perfusion (TRAP), talk to your doctor or obstetrician. Support groups are available for more resources and information.