Twin-to-Twin Transfusion Syndrome

What is twin-to-twin transfusion syndrome?

Twin-to-twin transfusion syndrome (TTTS) is a condition that happens during pregnancy in which 1 twin gives blood and nutrients to the other twin. It can happen in identical twins (or triplets) who share a placenta (monochorionic multiples).

Typically, each baby in the womb has its own vessels that carry blood and nutrients from the placenta to the baby and then back to the placenta again. Both babies get about the same amount of blood.

Illustrations showing a laser being used to treat twin-to-twin transfustion syndrome.

To treat TTTS, doctors often use a laser to close the abnormal blood vessels that let 1 twin get too much blood (right) while the other twin gets too little (left). The goal is to allow equal blood flow to both babies.

In TTTS, abnormal vessels in the placenta connect the babies’ circulation. These vessels let 1 baby (called the donor) pump blood to the other baby (called the recipient). The babies do not get an equal amount of blood. The donor gets too little, and the recipient gets too much.

About 1 in 7 monochorionic pregnancies develop TTTS. The condition can begin at any time during pregnancy. Doctors do not know why it happens. It is not caused by anything the parents did or did not do.

  • What are the risks of TTTS?

    The donor twin is at risk of not having enough water (dehydration), red blood cells (anemia) and amniotic fluid (oligohydramnios). Their bladder may be small or missing. They may not get enough nutrients or have enough space to grow well, and they may be smaller than their sibling.

    The other twin is at risk of getting too much blood (hypervolemia) and too much amniotic fluid (polyhydramnios). As extra blood overloads their heart and blood vessels, they may get hydrops and congestive heart failure.

    Without treatment, both babies are at high risk of dying in the womb. Another risk is going into labor too early before the babies are able to survive.

    With treatment, there is a strong chance 1 or more babies in the pregnancy may be saved. Babies who survive and are born after treatment for TTTS typically go on to live a full, healthy life.

Seattle Children’s Expertise and Care in Treating TTTS

Seattle Children’s Maternal Fetal Intervention and Surgery Program provides care and support for families with developing babies who have TTTS. This program is part of Seattle Children’s Fetal Care and Treatment Center. We have the only fetal intervention and surgery program in the Northwest.

  • An experienced, compassionate team
    • Drs. Bettina Paek and Martin Walker have done more than 1,000 fetal procedures over nearly 20 years. This includes more than 575 laser ablation procedures for TTTS, with some of the highest survival rates in the country. More than 96% of procedures result in one or both twins surviving, and more than 75% result in dual survival. See our TTTS outcomes.
    • Fetal therapy nurse coordinator, Melissa Dorn, MN, RN, has worked closely with both doctors for many years caring for families with TTTS.
    • Our specially trained sonographers are experienced in getting the images the doctors need to care for babies while they are still in the womb.
    • More team members, like genetic counselors, social workers and others, are here to offer services and support based on your needs.
    • This team provides highly specialized care with compassion. We understand the challenges your family is facing and create the most caring, seamless experience possible. We are here not only to provide technical expertise but also to help support you emotionally.
  • Care custom-made for your family
    • Each pregnancy is unique, even if your babies have a condition we have treated hundreds of times before. We make an individual care plan just for you. You can feel confident we are always looking after you and your babies’ interests.
    • When babies have health concerns serious enough to consider treatment before birth, families often need to make hard choices about what to do. We understand how difficult this can be. Our approach is to listen carefully to your values and needs, inform you about every option and answer your questions. We guide you so you can choose the right path for your family — and we support you, whatever you decide.
    • Based on your babies’ health, we work with the rest of your pregnancy care team to make special plans for delivery, if needed. If your babies are likely to need complex care soon after birth, we have a highly skilled neonatal transport team to transfer your newborn from your birth hospital to Seattle Children’s. Most babies with TTTS are born early and stay in the Neonatal Intensive Care Unit first.
    • After birth, specialists from across Seattle Children’s are here to provide any care your children may need, from their first hours and days through young adulthood. U.S. News & World Report has recognized Seattle Children’s as a top children’s hospital every year since it began ranking medical facilities more than 25 years ago, which means your child will be cared for by the very best.
  • Here when you need us
    • We are available 24 hours a day, 7 days a week, every week of the year, if you need care right away for TTTS. For urgent health concerns that might need intervention or surgery, we typically speak with you by telephone the same day you or your referring doctor contacts us. Often, we see families in person within 1 day and do intervention or surgery the same day or the next day.
    • We make it easy for you and your referring doctor to reach us. Usually, a referring doctor calls us, describes the health concern and sends us your details, like your imaging, test results and contact information. We review everything right away and call you, typically the same day, to talk about next steps.
    • The process is designed to be simple, seamless and hassle-free for you so you can stay focused on yourself and your family.
    • Families come to us from around the Northwest and beyond. Our social workers and Guest Services staff have a great deal of experience providing support with housing and transportation in the Seattle area, financial counseling, interpreter services, spiritual care and more. Read about our services for patients and families.
  • State-of-the-art facilities
    • For appointments with our Maternal Fetal Intervention and Surgery team, families come to our Fetal Care and Treatment Center in the Springbrook Professional Center, a block from our main Seattle hospital campus.
    • We have the advanced technology to provide the best care for you and your baby. At the same time, we have made the space comfortable, calming and warm. New consultation rooms mean you can stay in 1 place for your consultation.
    • For most TTTS procedures, an operating room is the safest place to provide care. Seattle Children’s specialists do these procedures in operating rooms at UW Medical Center–Montlake, less than 1 mile from Springbrook. Procedures that can be done safely in the clinic take place at Springbrook.
    • Your care team will explain where your procedure will take place and why. We will make sure you have all the details you need so your care goes as smoothly as possible — before, during and after your procedure.
  • Research to advance TTTS treatment
    • Drs. Bettina Paek and Martin Walker are founding members of the North American Fetal Therapy Network. This group brings doctors and scientists together to collaborate on research and education to improve care for babies before birth.
    • They have led or taken part in many research projects to learn more about the best ways to detect and treat a wide range of fetal conditions, including TTTS.
    • Paek has also published articles to teach other doctors about listening to patients and families, taking their values into account and helping them through difficult decisions and outcomes.

“The best part was going to Seattle Children’s, we went from being terrified to feeling comfortable. Seeing the same four people each time really helped.”
- Nic Hamston, father of twins June and Hazle who had twin-to-twin transfusion syndrome. Read their story.

What are the symptoms of twin-to-twin transfusion syndrome?

Pregnant people may not notice any symptoms from TTTS. Often, this condition is found during a routine ultrasound.

If your babies have TTTS, you might notice these sudden changes:

  • Your belly gets bigger or feels fuller, tighter or less comfortable.
  • You feel more fatigued.
  • You feel more pressure in your belly or back.
  • You gain more weight than normal for pregnancy.

How is twin-to-twin transfusion syndrome diagnosed?

To diagnose TTTS, doctors use ultrasound. They check if the babies share a placenta, and they look for differences in the babies’ size and the amount of amniotic fluid around each baby. They also look at blood flow in the babies’ umbilical cords, brains and hearts to tell how severe the condition is. Seattle Children’s has sonographers with special training in doing ultrasounds to find fetal conditions like TTTS.

To get more details, our pediatric cardiologists use fetal echocardiograms to check for effects on the babies’ hearts.

How is twin-to-twin transfusion syndrome treated?

After checking you and your babies and talking with you about imaging and test results, we consider all the treatment options and explain each option to you. We make sure you understand the options and all your questions are answered. The entire team is here to give you the information and support needed for you and your family.

  • Expectant management

    Before recommending a treatment plan, doctors take into account how severe the TTTS is. When there’s an imbalance in amniotic fluid but no sign of further problems, doctors sometimes recommend waiting before having treatment. In this case, it is important to have visits with the care team and ultrasounds to check the babies for signs of change. Even if no other treatment is needed, the care team may decide at some point that the babies will do best if delivered early.

  • Laser ablation

    This is the gold standard for treating TTTS that starts early in pregnancy (about the first 26 weeks). To stop blood flow from the donor twin to the recipient twin, doctors do laser ablation, also called fetoscopic laser surgery or fetoscopic laser photocoagulation. They close the abnormal blood vessels in the placenta using light to heat and break down small amounts of tissue. The goal is to allow equal blood flow from the placenta to both twins so both have the chance to recover.

    Most families who come to Seattle Children’s with TTTS have this treatment. See our outcomes for laser ablations in TTTS.

    Seattle Children’s maternal-fetal surgeons do this minimally invasive surgery in an operating room at UW Medical Center–Montlake. It involves making a small incision in your belly (3 millimeters, or about the thickness of 2 pennies). Through this hole we can insert a thin tube with a camera (fetoscope), as well as a laser probe. The camera lets the doctors see the abnormal blood vessels. After sealing these vessels, we drain the extra amniotic fluid around the recipient twin.

  • Serial amnioreduction

    Amnioreduction is using a needle to take out amniotic fluid. This can be done if there is too much fluid around 1 twin. It does not fix the uneven flow of blood in TTTS, but it may help with some of the effects. It’s typically used only in mild cases that start later in pregnancy. Often, excess fluid builds up again over time, and doctors need to repeat the procedure (serial amnioreduction). We do this procedure at Seattle Children’s Fetal Care and Treatment Center earlier in pregnancy and at UW Medical Center–Montlake later in pregnancy, using ultrasound to guide the needle. Some families go on to need laser ablation later in the pregnancy.

  • Bipolar cord coagulation

    If TTTS or another health concern is so severe that 1 baby is not going survive, doctors can stop blood flow to this baby to get the best outcome for the other baby. They can do this using a small tool to deliver an electric current that heats and seals blood vessels in the umbilical cord.

    As with laser ablation, our maternal-fetal surgeons do this minimally invasive surgery through a small incision in your belly. Through this hole we can insert a thin tube with a camera (fetoscope) and small surgical tools. The surgery takes place in an operating room at UW Medical Center–Montlake.

  • Follow-up care

    After treatment for TTTS, the Maternal Fetal Intervention and Surgery team makes sure you know what to expect next. If you had a procedure here, we give you details about recovering. We also share information with your referring pregnancy care providers so they have what they need to keep caring for you.

    If you live nearby, we see you weekly for at least a month after your procedure to check your babies’ health. If you live far away and this is not convenient for you, we recommend you see your referring provider weekly.

    Even when TTTS treatment works, most of these babies are born early (prematurely). Premature babies may need special medical care in the weeks and months right after birth (and sometimes longer). A small number of babies (about 1 in 20) born after TTTS treatment have lasting neurological effects from TTTS. Seattle Children’s has a full range of specialists to provide the care your child may need from infancy to young adulthood.

Contact Us

Contact the Fetal Care and Treatment Center at 206-987-5629 for an appointment, second opinion or more information.

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