Children's Hospital Colorado

Twin-to-Twin Transfusion Syndrome (TTTS)

What is twin-to-twin transfusion syndrome (TTTS)?

Twin-to-twin transfusion syndrome (TTTS) is a disorder that affects identical twin pregnancies. It can occur when two fetuses share a placenta (referred to as a monochorionic twin pregnancy) because there isn’t a barrier separating the two fetuses from each other.

Sometimes, blood vessels from the twins' umbilical cords form abnormal connections within their shared space, connecting one baby to the other. When this happens, blood flows unevenly between the babies and their circulations become unbalanced. This puts the twins at risk for early delivery, neurological damage and more.

Twin-to-twin transfusion syndrome (TTTS) is a serious, rare condition only seen in identical twins who share a placenta (monochorionic).

One fetus (called the "donor" twin) "donates" their circulation of fluid and blood to the other fetus (known as the "recipient"). As a result, the donor twin may stop producing urine and its amniotic sac becomes much smaller.

The recipient twin receives too much blood and urine and produces more amniotic fluid, resulting in having a very large amniotic sac.

TTTS can lead to severe complications for the twins. That's why early detection is critical to help improve outcomes for both babies and their mother.

What causes TTTS in pregnancy?

The exact cause of TTTS is not well understood; there are no known genetic causes of TTTS, and there's nothing a mother did to cause it. In the majority of cases, TTTS develops in the second trimester of pregnancy.

While there's nothing anyone can do to prevent TTTS, there's plenty we can do to help your babies. The important thing that families can do when they are diagnosed with monochorionic-diamniotic twins is to have close and early surveillance for TTTS, specifically by having ultrasounds every two weeks starting at 16 weeks of gestation.

Who gets TTTS?

TTTS can affect identical twins before they are born. Approximately one in every 250 pregnancies are identical or monochorionic and approximately two out of three of these pregnancies are monochorionic diamniotic, meaning the fetuses share a placenta but have two separate amniotic sacs. Of these pregnancies, 10 to 15% develop TTTS.

Although less common, TTTS can happen in monochorionic monoamniotic twins where the twins are in one sac without a dividing membrane.

The Connection Journey
Beating the TTTS odds, together

Our fetal experts can tell parents a lot about their babies' TTTS and treatment to come. One thing they can't often tell them: how they will feel. Nicole and Ari share their experience with TTTS, offering hope as Alyssa and Mark navigate their unborn babies' TTTS journey.

Watch their stories

What are the signs of TTTS?

There are not many outward signs of TTTS, as it is diagnosed by ultrasound.

Does the mother show any signs of TTTS?

In many cases a mother may not experiences symptoms of TTTS. However, some mothers whose twins have TTTS will feel signs of excess amniotic fluid.

The signs and symptoms a mother may experience include:

  • A uterus that measures large for her stage of pregnancy
  • Feeling like her abdomen is growing or expanding rapidly
  • A sudden increase in body weight
  • Increased abdominal pressure or pain
  • Shortness of breath
  • Uterine cramping or contractions
  • Swelling of the hands and legs early in the pregnancy

If you're pregnant with twins and feel any of these symptoms, contact your doctor immediately for further evaluation.

What are the potential effects of twin-to-twin twin transfusion syndrome?

Because of their differing blood supplies, each baby will face a different set of challenges and potential complications requiring expert care.

The complications that may occur when your twins have TTTS include:

  • Selective intrauterine growth restriction (sIUGR): A more complicated state of TTTS where one baby may only have a small amount of the placenta
  • Cardiomyopathy
  • Premature labor
  • A condition called twin anemia-polycythemia sequence (TAPS), where one fetus has a low blood count and the other has high blood count
  • Loss of one or both fetuses

At the Colorado Fetal Care Center, our fetal surgeons are available for consultation and treatment 24 hours a day, seven days a week. This round-the-clock service is important for a mom and her babies, as the outcomes of fetuses with TTTS vastly improve with early treatment. Our maternal and fetal medicine specialists are skilled in addressing the complications that may affect one or both twins.

Potential TTTS effects in the recipient twin

With TTTS, the recipient twin is receiving more fluid and their heart is pumping against higher blood pressure. As a result, they're producing too much urine, which causes a significant increase in amniotic fluid. Other potential problems can occur in the recipient, including:

  • Heart failure
  • Demise or loss of the twin

Potential TTTS complications in the donor twin

Lacking fluid and blood, the donor twin has less volume and produces less urine which causes a small amniotic sac. Other complications may occur, including:

  • Weighing less than expected, a complication known as intrauterine growth restriction (IUGR) or fetal growth restriction (FGR)
  • Demise or loss of the twin

How does TTTS affect each twin?

The donor baby has signs of dehydration, such as little to no urination, which leads to low amniotic fluid levels. (Urine is what makes up the majority of the amniotic fluid that surrounds a baby.)

The recipient baby experiences signs of over hydration, including increased urination, which leads to high amniotic fluid levels. Sometimes, the recipient baby may show signs of fetal heart failure.

If TTTS is left untreated and becomes severe, there could be severe complications for the babies, including brain injury, heart damage or death.

What happens if the mother loses a baby?

If TTTS causes just one of the twins to survive, it’s important that mothers know this is not their fault.

In this case, the surviving twin is at risk for brain and other organ damage, as pumping blood back to the deceased twin deprives the surviving twin of blood, oxygen, fluids and nutrients. Quick intervention by experienced TTTS experts is critical to give the surviving twin their best chance at a positive outcome.

How is TTTS diagnosed?

TTTS is diagnosed by ultrasound. The earlier the disease is diagnosed – specifically when the disease is in its early stages – the better the prognosis. And the sooner we’re able to intervene – ideally within hours of diagnosis – the better the chance is for a positive outcome.

If you're pregnant with monochorionic-diamniotic twins, we recommend you are evaluated via ultrasound at least every two weeks throughout your pregnancy once you have hit 16 weeks.

What happens after my babies are diagnosed with TTTS?

If your twins show signs of TTTS, our multidisciplinary team will perform a complete evaluation including several fetal diagnostic tests. With this one-day evaluation, you’ll:

The evaluation consists of:

  • Imaging your babies with a complete anatomy ultrasound by your high-risk obstetrician
  • An ultrasound of the heart (echocardiogram) by our fetal cardiologists
  • A fetal MRI if necessary

Based on your babies' ultrasound results, your care team will diagnose the severity of the twin-twin transfusion.

Determining TTTS treatment options together

The fetal medicine specialists at our Colorado Fetal Care Center focus on each mother's and baby's unique case. We provide mothers with clear counseling on:

  • TTTS as a condition
  • The specific severity of her twins' disease
  • Options and recommendations for treatment
  • Anticipated outcomes

Together, we will create a specialized treatment plan to ensure the best outcomes for you and your babies.

What are the treatment options for twin-to-twin transfusion syndrome?

At the Colorado Fetal Care Center at Children's Hospital Colorado, our doctors are experts at identifying and treating twin-to-twin transfusion syndrome.

We understand that receiving a TTTS diagnosis during your pregnancy can feel life-changing, but you'll have an entire team taking care of you and your twins so that it isn’t. Our state-of-the-art facilities, extensive experience treating this condition and innovative treatment options may help your children thrive, both during pregnancy and after birth.

Time is critical when it comes to treating TTTS. The earlier this condition is caught, the more easily it can be treated. Many treatment options can be started within hours or days of diagnosis.

Twin-twin transfusion treatment options include:


In cases of TTTS where the recipient baby shows signs of heart dysfunction, such as cardiomyopathy or hydrops, we can use a high blood pressure medication called Nifedipine.

This is a non-invasive, interventional method meant to stabilize the disease while we wait for other therapeutic options. The Nifedipine spreads through the mother’s bloodstream, crossing through the placenta to help her babies’ hearts.


An amnioreduction is a procedure where a doctor removes the extra amniotic fluid in the amniotic sac using a small needle with ultrasound guidance. The doctor will remove fluid until a mother's fluid levels return to normal.

Our fetal surgeons perform an amnioreduction to help prevent preterm delivery and any other complications related to polyhydramnios (too much amniotic fluid). The potential benefits of this TTTS treatment option include:

  • Decreasing a mother's abdominal pressure
  • Slowing the progression of the disease
  • Improving blood flow between the babies
  • (In rare cases) halting or even reversing the TTTS

Laser TTTS surgery

In severe cases of TTTS, our fetal surgeons will recommend laser surgery. When this is the best treatment option, we will ordinarily perform this minimally invasive fetal intervention within 24 to 72 hours of your evaluation.

The laser TTTS surgery, called Selective Fetoscopic Laser Photocoagulation (SFLP), takes place in a dedicated operating room within the Colorado Fetal Care Center, so your preoperative care, surgery and postoperative care will all take place in one location. Most of our mothers have an epidural before the surgery is started to ensure a painless procedure. We have dedicated fetal anesthesiologists who is by your side every step of the way.

To perform the laser procedure, we insert a small camera into the uterus, under ultrasound guidance. We use this camera to identify the abnormal blood vessel connections between the babies. Then, we use a small laser device to block the abnormal vessel connections and definitively stop the harmful blood flow between the babies.

We usually also perform an amnioreduction after the laser to remove any excess amniotic fluid.

Why choose the Colorado Fetal Care Center for TTTS diagnosis and treatment?

88% Overall survival
LEADER In using Nifedipine for TTTS treatment
84.6% Survival rate of one or both twins

When coming to the Colorado Fetal Care Center for TTTS treatment, parents can expect an unparalleled level of quality, coordinated care. In fact, we are one of the nation's top care centers for the treatment of pregnancies complicated by TTTS.

That's because due to our 24/7 care model, our care and expertise is never out of reach. We're here to handle whatever need you or your baby may have, no matter the time or day or night. Our Center is always staffed with the pediatric, neonatal and maternal fetal experts you need to handle high-risk pregnancy and TTTS complications.

Not only do we offer some of the most innovative fetal therapies around, but we’re constantly advancing the field. Because TTTS is a complicated disease and its causes are not yet understood, we collect detailed information on every TTTS pregnancy and investigate the underlying causes. This helps optimize the outcomes for our patients.

A continuum of care: comprehensive treatment for TTTS

We understand the stress and fear that can come from learning your babies have TTTS. This is why we have specialized maternal and fetal medicine experts for every aspect of you and your babies’ care.

Additionally, we're one of the few centers that brings together the full multidisciplinary care team from the very beginning, ensuring the most responsive and comprehensive care plan – before and after birth.

And with a Level IV NICU and world-class pediatric experts right here on the Anschutz Medical Campus, we're able to ensure a smooth transition between the various providers involved in your care and any specialists your babies may need.

A multidisciplinary team of TTTS experts dedicated to you and your babies 

At the Colorado Fetal Care Center, you will meet the various team members who are all dedicated to you and your babies. Each person plays a unique role in the coordination of care, evaluation of your pregnancy, diagnosis of your babies' condition, counseling of treatment options and treatment of your disease. We also educate our patients to integrate themselves into their own care team, so they're informed every step of the way.

During your appointment, you will meet nurse coordinators, medical assistants, fetal sonographers, fetal ultrasound specialists, anesthesiologists, fetal cardiologists and fetal surgeons, including pediatric surgeons and maternal fetal medicine specialists. Learn about your visit to our Center.

And when it comes to treatment and procedures, you will be treated by dedicated TTTS specialists, including fellowship trained fetal surgeons, who have trained specifically and extensively for these procedures. Our expertise in treating TTTS means the best chance at a positive outcome for you and your babies. Take a look at our most recent fetal surgery and TTTS outcomes.

But experience at the Colorado Fetal Care Center goes beyond the medicine – we have care coordinators, social worker and staff to ease the stress and burden of a TTTS diagnosis.

We attend to you and your family's needs, emotional or otherwise, and provide a personalized approach to navigating the entire process, including scheduling. In addition, we help coordinate the travel and stay for each patient while they are here.

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