Twin-to-Twin Transfusion Syndrome (TTTS)
Diagram of twin-to-twin
What is a Twin-to-Twin Transfusion Syndrome (TTTS)?
Twin-to-twin transfusion syndrome is a rare complication that develops in up to 15% (Y. Ville, 2005) of identical twin pregnancies when the babies share a common placenta. It may begin in the second or third trimester. This phenomenon is related to an abnormality in the placenta itself. Communicating blood vessels on the placenta cause a disproportionate flow of blood between the twins. One baby donates more blood to the other and becomes smaller, or 'donor'. The other twin, receiving extra blood, becomes larger and is called the 'recipient'. The health of both babies is at risk. The 'donor' twin has less blood flow which leads to poor growth and decreased blood flow to the brain and kidneys. The 'recipient' twin has increased blood flow that may result in cardiac and neurological problems.
The cause of TTTS is unknown.
What testing is recommended during the pregnancy?
Serial ultrasounds are necessary to monitor the health of both babies. Fetal echocardiograms are needed to evaluate the heart function of both babies. A fetal MRI may be recommended if there are other suspected problems. An amniocentesis is offered to assess a karyotype for both babies.
Are there special considerations planned for the delivery?
It is recommended that the delivery of the babies is planned at a hospital that is prepared for high-risk deliveries, including a neonatal intensive care unit. Preterm labor is common with TTTS. A Cesarean delivery is recommended only if indicated for obstetrical reasons.
Is there fetal treatment for TTTS?
An endoscopic laser procedure can be performed between 16 and 26 weeks gestation when recommended. This procedure uses a fetoscope (tiny medical telescope) and a laser fiber. The telescope is used to identify the connecting blood vessels on the placenta that are causing the problem. The laser is directed at the problem vessels and used to coagulate, or seal them off. For more information about fetal laser intervention, please click here.
There are other procedures used for TTTS that do not treat the underlying cause of the syndrome, but address some of the side effects caused by the uneven blood flow. Amnioreduction is a procedure that removes some of the amniotic fluid from the sac of the larger twin.
A septostomy is a procedure that makes tiny holes in the membrane that divides the twins. This permits fluid to pass through in an attempt to equalize the quantity of amniotic fluid for each baby.
In select cases, the blood flow to one baby is selectively obstructed, giving the other baby a better chance of survival.
Some families choose no intervention and allow nature to take its course. Left untreated, the mortality rate for both twins approaches 90% (Senat, Deprest, Boulvain, Paupe, et. al. 2004). Treatment options are complex and need to be individualized for each patient.
Are there other health problems that are more common among babies with TTTS?
Many babies with TTTS are born prematurely therefore their overall health is usually dependent on their gestational age. The babies are at risk for neurological, cardiac and kidney problems.
Any infant that requires an extended stay in the neonatal ICU will often have developmental delay and other health problems.
Can this happen again with another pregnancy?
The risk of TTTS in a subsequent pregnancy is extremely low. Your doctor and a genetic counselor will review the risk in your family.