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Twin to Twin Transfusion Syndrome (TTTS)

What is Twin to Twin Transfusion Syndrome (TTTS)?

Twin to Twin Transfusion Syndrome (TTTS) is a problem with the blood flow between identical twins who share one placenta.

In about 9 out of 10 pregnancies, identical twins with one placenta share equally and no problems arise. However, in 1 of 10 identical twin pregnancies with one placenta, the twins do not share blood equally.

Because of the unequal blood flow, one twin gives more blood to the other twin than it gets back. The twin that keeps giving more blood is the donor twin. The twin that gives back less blood than it gets is the recipient twin.

This can cause problems for both babies. The donor twin may have low blood levels and underdeveloped organs. The recipient twin's heart has to work harder to process the extra blood, and may also have extra fluid in their amniotic sac.

Diagnosing TTTS

TTTS is usually discovered through ultrasound at around 20 to 22 weeks. However, it can be diagnosed as early as 15 weeks and as late as 36 weeks. Women who are pregnant with identical twins who share a placenta are generally scheduled for ultrasounds every two weeks beginning at 15 to 16 weeks and continuing throughout the pregnancy, even if there are not problems with blood flow between the twins.

Ultrasounds identify changes in TTTS

These regular ultrasounds helps to find changes that may indicate TTTS is present or progressing in the pregnancy.  Doctors use stages to describe the severity of the TTTS. This helps your care team identify the best course of treatment for you and your babies.

Stage 1: 

The donor twin has low fluid (low amniotic fluid around the baby), while the recipient twin has high fluid.

Stage 2: 

The donor twin’s bladder cannot be seen by ultrasound. This twin has a bladder but is not making urine.

Stage 3: 

One or both twins are found to have abnormal blood movement through the umbilical cords, through the fetal livers (a blood vessel called the ductus venosus) and through the fetal brains. The changes in the blood flow through the babies are because the donor twin has low blood levels and the recipient twin has high blood levels. 

Stage 4: 

One or both babies have heart failure. Heart failure for a twin with TTTS is found by ultrasound. The baby will have extra fluid found under the skin, around the lungs, around the heart or around the intestines. 

Stage 5: 

Loss of one or both twins. 

Treating Twin to Twin Transfusion Syndrome

There are two common treatments for Twin to Twin Transfusion Syndrome.

Amnioreduction is a procedure where the doctor places a needle into the amniotic sac (bag of water) of the larger, recipient twin. This allows the doctor to remove excess fluid from the bag of water. The doctor uses ultrasound to guide the placement of the needle.

Removing extra fluid can help decrease pressure, improve the blood flow between the twins, and sometimes slow the progression of the TTTS. However, nine out of 10 times, the fluid will return. This is why it is important to continue with ultrasound evaluations to watch the fluid levels for both twins.

Laser treatment is often the best option for severe TTTS because it treats the problem rather than just addressing the symptoms. This surgery, known as Selective Fetoscopic Laser Photocoagulation (SFLP), uses a small laser device to close off all the shared blood vessels between the twins, so that they each have an independent connection to the placenta. This procedure is usually done between 16 and 26 weeks gestation.

During the SFLP procedure, your doctor will use ultrasound guidance to place an endoscope (small camera instrument) in the bag of water of the larger, recipient twin. This allows the doctor to map all the blood vessel connections on the placenta that are shared between the twins. Using the map of the shared blood vessels, your doctor uses a laser fiber to burn (photocoagulate) all the shared connections, sealing them off.

Once all these shared blood vessels are sealed, the doctor makes a thin line of laser burn, connecting all the places where the blood vessels were sealed. This stops the blood flow of any very tiny blood vessels that may be too small to see.

At the end of this procedure, your doctor will do an amnioreduction to bring the amniotic fluid to a normal level. Most moms are able to go home the next day, though this varies.

Monitoring TTTS during pregnancy

Whether you have amnioreduction or laser therapy, your care team will continue to monitor your babies' fluid and blood flow through frequent ultrasounds. Right after treatment, you may have ultrasounds once or twice a week until the twins are stable. Then, we'll continue to monitor them every week or two for the rest of the pregnancy.

What to expect during treatment

Considering your treatment options and deciding on the right path for your family is a lot to manage. Rest assured that your doctor, nurse coordinator, sonographer, and the whole Fetal Health Center team will be with you every step of the way.

Find out more about what to expect when you choose Children's Mercy for your family's care.

Choosing the best home for your child's care


TTTS can progress quickly and become an urgent matter for both babies. At the Fetal Health Center, we take a team approach that allows our experts to come together and move quickly to create a care plan that is right for you and both babies.

If you and your doctors feel like it would be beneficial, you can deliver your babies in the Special Care Delivery unit, located within the Fetal Health Center at Children's Mercy. That way, your babies can receive immediate, expert care from our neonatologists, and you and your family can be right there with them.

Your babies will have every support they may need in our Level IV NICU, the region's highest-level care center for newborns.

Other families prefer to continue care with their primary care provider or obstetrician once the procedure to stabilize the twins is complete. Either way, your Fetal Health Center team will work closely with your primary care providers to ensure everyone is part of the care plan.

Most twins who receive fetal therapy for TTTS are delivered between 32 and 36 weeks of pregnancy. Research supports this timeframe as the best option for safe delivery. You and your doctor will discuss whether to delivery vaginally or by cesarean section, depending on your circumstances and preferences.

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