Diagnosed with TRAP


From Pregnancy Through Diagnosis and Treatment

What is TRAP?

Twin reversed arterial perfusion  (TRAP) is a form of TTTS that affects twins that share a common placenta (monochorionic). It is defined when one healthy twin has a cardiovascular system that is used to pump blood through the placenta keeping the other twin alive who has sadly, not completely formed physically and lacks a functioning cardiovascular system.  In medical terms, this baby is referred to as the acardiac twin whereas the other baby is the pump twin.  Due to this lack of physical development, including parts of his or her body and vital organs, the acardiac baby cannot survive outside the womb.



Diagnosed with TRAP

During this very difficult time, we are here to surround you with support.  We will help you. You are not alone.

How is TRAP Diagnosed?

When a woman finds out she is pregnant, she should get an ultrasound by 6-8 weeks to determine if she is pregnant with twins and if so, to determine if there is one placenta or two.  If there is one placenta, then TRAP is a possibility although a very low risk of about 1%.  With monochorionic twins, you must be in the care of a high-risk maternal-fetal medicine specialist (MFM).  With the use of 3-D and 4-D ultrasound and doppler blood flow patterns, TRAP may be diagnosed as early as 11 weeks.  It is also always important to have your placenta analyzed at birth.

Dr. De Lia Conferernce


Read The TTTS Foundation's 15 Most Important Questions You Need To Ask Your Doctor Today

What does Twin Reversed Arterial Perfusion Mean?

Normally, arteries carry blood from a baby to the placenta to receive oxygen from the mother’s circulation and veins return the blood back to the baby.  With TRAP, however, due to the artery to artery connections in the shared placenta, the blood in the artery of the underdeveloped baby flows in a reversed direction  not to the placenta, but back to the underdeveloped baby.  This happens because the healthy twin’s artery perfuses or merges into the underdeveloped baby’s artery reversing the direction of flow back to the baby and creating their source of  nutrients and oxygen to grow.  The acardiac baby does not have beating heart to pump blood to the placenta and through its own body. Thus, all of the blood supply to the acardiac baby comes only from the circulation of the healthy twin.

Figure 2. This is a placenta from a TTTS pregnancy treated with reduction amniocenteses that delivered at 27 weeks’ gestation. The donor and recipient sides of the placenta are labeled, and their umbilical cords are seen with plastic clamps attached. This placenta was equally shared by the twins and contained three artery-to-vein connections (arrows) between the twins which joined in the region of the vascular ‘equator.’ (Photo courtesy of Dr. Julian E. De Lia)


For an In-Depth Understanding of the Monochorionic Twin Placenta

How is My Healthy Twin Affected by TRAP?

Overloaded Cardiovascular System

The heart is our largest muscle.  When we work our muscles, they get bigger.  With TRAP, the heart of the healthy twin can enlarge.  The healthy baby’s cardiovascular system can become overloaded.  The baby can go into heart failure if the underdeveloped twin becomes too large.  This seems to be less of a risk if the baby is less than 50% the size of the healthy twin.  In summary, blood is pumping from the healthy twin through the shared arterial blood vessels in the placenta to pump blood in a reverse direction to the acardiac baby.  The healthy twin is at risk for heart failure depending on the size of the other baby.

If the healthy baby is on overload pumping more blood, he or she will also increase blood flow to the kidneys.  This potentially increasing urine output, which is basically amniotic fluid, which in turn, may increase the risk of a premature birth.  It all depends on the size of the other baby.  Again, if on the smaller size, none of these warning signs will be seen.

Create your Medical Plan of Action Today

What Tests do I Need?

With TRAP, you will need weekly ultrasounds to measure weights and get dopplers of the blood flow patterns.  There is a continuous flow of blood from the normal twins’ artery to the placenta, and then a reverse flow in the underdeveloped baby’s artery in the placenta.  This allows blood to continue to flow all the way through the underdeveloped baby’s body and back again to the normal baby.  For this reason, you will need to watch the healthy twins’ heart frequently with echocardiograms.

What to Know about My Babies?

That they both love you with all their heart and you will always be a mother of twins.

Meet our TRAP coordinator.

December 10th is World TRAP Awareness Day.  Kristen shares her experience.  At 30 weeks, Ethan had stopped growing and Kristin delivered by emergency C-section. Ethan needed a lot of help. He had a perforated colon and needed surgery for several heart defects. He is now a healthy 7 year old loved by his whole family.

Twin to Twin Transfusion Syndrome is a powerful disease, but it's not stronger than a mother's love.