Twin to Twin Transfusion Syndrome

Twin to twin transfusion syndrome (TTTS) is a prenatal condition that can affect the pregnancy of twins in which two fetuses share a placenta (monochorionic). Usually, each twin has his/her own gestational sac (diamnionic). It is rarely seen in triplets.

About 70 percent of identical twins share a placenta; up to 20 percent of these pregnancies experience TTTS. There are different stages of TTTS, some of which are more serious or difficult to treat. The cause of TTTS is not completely clear.

In TTTS, one of the fetuses, identified as the donor, receives less blood flow. This fetus grows slower and is smaller, and can become dehydrated and produce less urine. This causes the bladder to be smaller and can cause a decline in amniotic fluid (oligohydramnios). The other twin is known as the recipient. This fetus will receive the higher blood supply and it can cause the baby to develop high blood pressure and produces too much urine. The consequence is the development of excessive amniotic fluid (polyhydramnios).

In mild cases, no treatment (expectant management) or the removal of the amniotic fluid (amnioreduction, called also therapeutic amniocentesis) may be options for the patient. In severe cases, in-utero intervention, such as laser ablation, may save the lives of one or both of the twins. University Hospitals is the first center in the region to use fetoscopic laser surgery to treat TTTS in-utero.

How Do We Diagnose TTTS?

Signs of TTTS are usually spotted on a routine prenatal ultrasound. A maternal-fetal medicine specialist can provide a more definitive diagnosis through a series of tests, including measurement of the amniotic fluid volume, bladder activity, and blood flow in both twins. The heart of both twins is examined with a fetal echocardiogram.

The fetal specialist will diagnose the severity of TTTS by categorizing it as one of four stages, ranging from mild to severe:

• Stage I: One twin has an excess of amniotic fluid while the other does not have enough.
• Stage II: The bladder of the “donor” twin is not visualized.
• Stage III: There is abnormal Doppler in one or both twins.
• Stage IV: There is hydrops (fluid buildup in a baby's tissues and organs that causes swelling) in one of the twins, usually in the “recipient” twin.

Treatment for TTTS

For the mildest forms of TTTS, physicians will begin with observation. Stage I can remain stable, resolve, or become more severe. If warranted, your physician may recommend amnioreduction, which drains amniotic fluid from the twin with excess fluid.

For more severe TTTS, our team can perform fetoscopic laser surgery. With laser surgery, the mother will be placed under IV sedation with local anesthetic and possibly an epidural. Then the surgeon will make a small incision in her abdomen and insert a small metal tube (called a trocar) into the uterus. The surgeon guides a fetoscope through the tube in order to view the blood vessel connections on the placenta and identify the abnormal connections. The laser is used to seal and disconnect those vessels. The surgeon will also drain excess amniotic fluid through the metal tube.

A few days after the surgery, the care team will follow up with tests such as ultrasound and fetal echocardiography to assess both twins’ conditions. Follow-up care will continue once the mother returns home and throughout the remainder of her pregnancy.

Even with successful treatment, TTTS can cause premature birth that may require a neonatal intensive care unit (NICU) stay. The majority of twins successfully treated for TTTS will live normal healthy lives, or have mild symptoms such as anemia. However, more serious problems such as neurological or heart-related conditions can sometimes occur and may require further care during infancy and childhood (in approximately 8 percent of cases).

Our Experience

The specialists at UH have pioneered the management of TTTS since 1987, when not much was known about diagnosis and management. Our team has used amnioreduction since 1987 and has provided follow-up care up to nine years following birth. They have also guided a register on TTTS with 19 other leading medical centers from different areas of the world. Our doctors have used laser surgery to treat TTTS since 2004 and trained current leaders both in the U.S. and abroad using laser surgery and other in-utero intervention.