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Twin-to-Twin Transfusion - Causes, Symptoms, Diagnosis, and Treatment

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Twin-to-twin transfusion syndrome (TTTS) is a condition that rarely occurs in identical twins during pregnancy or gestation. Read to know more about it.

Written byDr. Osheen Kour

Medically reviewed byDr. Veerabhadrudu Kuncham

Published At March 30, 2023
Reviewed AtAugust 30, 2024

Introduction

Twin-to-twin transfusion (TTTS) is a disease or an abnormality of the placenta that affects the health of each twin in a different way. The condition is rare but severe and only occurs in identical twins with a common placenta. The single placenta passes through both the twins and contains blood vessels which usually carry a balanced blood supply to both babies. However, in the case of twin-to-twin transfusion, this balance is disturbed as the blood flows from one twin (donor twin) to the other (recipient twin). This leads to an unequal blood exchange and thus can cause a risk of heart failure, the oversize of the recipient twin, and the accumulation of excess amniotic fluid around this twin. On the other hand, the donor twin is smaller due to a lack of enough blood, and also it produces very little urine, which makes the bladder invisible on the ultrasound. There are treatment options available for twin-to-twin syndrome, but if the condition is left untreated, the survival rate of twins may decrease to less than 10 percent.

What Are the Causes of Twin-to-Twin Transfusion?

The exact cause of twin-to-twin transfusion syndrome is unknown. It is an irregularity of the placental that occurs during gestation and is a congenital defect. The syndrome arises due to the blood movement from one twin to the other through the common placenta. As a result, the twin that receives the blood supply is called the recipient twin, and the one that loses the blood is known as the donor twin. This causes an imbalance in the blood flow between the twins, which is usually fairly balanced, and thus causes twin-to-twin transfusion syndrome (TTTS).

What Are the Symptoms Shown by the Mother in the Case of Twin-to-Twin Transfusion?

The mother usually experiences symptoms because of the excess of amniotic fluid accumulation around the recipient twin. The symptoms include

  • Pressure in the stomach.

  • Breathlessness.

  • Rapid weight gain.

  • Premature contractions.

  • The rapid expansion of the abdomen or tightness in the abdomen.

How to Diagnose Twin-to-Twin Transfusion?

The doctor can diagnose twin-to-twin transfusion during a regular prenatal ultrasound. The condition can occur at any time during the pregnancy and is more severe during the early phase of pregnancy when delivery is impossible. The doctor conducts various diagnostic tests for suspected problems during routine checkups and ultrasounds. The pediatric cardiologist performs a special ultrasound test called a fetal echocardiogram to check a fetus’s heart and blood vessels carefully.

The ultrasound findings suggest that suggest pregnancy needs to be closely monitored as follows:

  • Same-gender twins.

  • Differences in size in twins.

  • Single placenta.

  • A dividing membrane that is thin and not clear.

  • Excess of amniotic fluid or polyhydramnios in one of the twin’s sacs.

  • Decreased or no amniotic fluid or oligohydramnios in the other twin’s sac.

In addition, fetal MRI (magnetic resonance imaging) is also performed to look for any injury to the brain that may be caused due to twin-to-twin transfusion syndrome (TTTS).

The severity of TTTS is further diagnosed with the Quintero staging system on a scale of one to five, where five is the most severe form.

Staging of Twin-To-Twin Transfusion Syndrome:

  • Stage I: There is a major difference in the amniotic fluid levels. One twin has an excess of fluid, and the other has very less fluid in the sac.
  • Stage II: The bladder of the donor twin is not visible on the ultrasound in stage II and the difference in amniotic fluid levels also persists.
  • Stage III: This stage is marked by an abnormal blood flow through the blood vessels or umbilical cord around the heart of one or both twins, along with an empty donor bladder and abnormal amniotic fluid levels.
  • Stage IV: In this stage, fetal hydrops are formed along with the above abnormalities. Fetal hydrops is the collection of amniotic fluids in body cavities in one or both twins.
  • Stage V: Loss or death of one or both twins.

The severity of the recipient babies’ heart condition is also evaluated through fetal electrocardiogram and marked as mild, moderate, or severe.

How Is Twin-to-Twin Transfusion Treated?

There are very few options available to treat twin-to-twin transfusion syndrome. Therefore, the doctor suggests fetal intervention methods only in the most severe cases. In some cases, if the TTTS occurs during the third trimester, premature delivery is the suggested option rather than fetal intervention, as it can cause complications in the pregnancy. The treatment plans are as follows:

  • Monitoring the Pregnancy: Less severe cases do not require surgical intervention, and the fetus is monitored with ultrasounds and electrocardiograms. In case of any worsening condition, the best treatment plan or early delivery is usually planned depending on the stage of pregnancy and severity of the condition (TTTS).

  • Amnioreduction: In this method, the excess of amniotic fluid is drained from the recipient fetus’s sac if the twins are not severely affected by twin-to-twin transfusion. If the amnioreduction method is ineffective, the doctor suggests laser surgery, also known as selective fetoscopic laser photocoagulation (SFLP).

  • Laser Surgery: This method is also known as selective fetoscopic laser photocoagulation. A small incision is made in the mother’s abdomen up to the uterus with a small metal tube or trocar. The fetoscope is then passed through this metal tube to view the shared placenta and other blood vessels on the placental surface.

What Is the Differential Diagnosis for Twin-to-Twin Transfusion?

  • Premature rupture of membranes (PROM).

  • Amniotic fluid discrepancies.

  • Selective fetal growth restriction (SFGR).

  • Preterm premature rupture of membranes (PPROM).

  • Twin anemia.

Conclusion

Twin-to-twin transfusion syndrome is a rare prenatal condition affecting twins' growth rates due to unequal placental blood supply. The condition does not occur due to anything related to the mother in any way. Almost 70 percent of identical twins have a shared placenta, and 15 to 20 percent of such pregnancies are usually affected by twin-to-twin transfusion syndrome. TTTs cases that are not treated timely during gestation cause 90 % fatality of twins after delivery, and almost 15 % to 50 % of them are at risk of developing neurological disorders. Therefore, the doctor's timely intervention is important to avoid future complications in the pregnancy.

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Frequently Asked Questions

Twin-to-twin transfusion syndrome is a rare medical condition that can occur in about 10 to 15 percent of mothers with monochorionic twin pregnancies. In this condition, there will be an imbalance in the blood flow that is caused due to placental vessel connections.

A person who has taken an appropriate treatment for twin-to-twin transfusion syndrome during pregnancy will survive by living a normal and healthy life. However, in untreated cases, the survival rate may vary from approximately 10 to 15 percent.

Usually, twin-to-twin transfusion syndrome develops between week 16 to week 26 during the pregnancy period. It can be diagnosed during 10 to 14 weeks by measuring the amniotic fluid level through an ultrasound scan.

Twin-to-twin transfusion syndrome may result in a large bladder, increased amniotic fluid level(polyhydramnios), and hydrops(a prenatal form of heart failure). All these outcomes are caused due to the overproduction of urine by the recipient twin due to increased blood volume.

In stage 3 of twin-to-twin transfusion syndrome, there will be abnormal blood flow patterns, including reversed umbilical artery end-diastolic velocity (UAEDV) and reversed flow of blood in ductus venosus (DV). This abnormal blood flow pattern indicates dysfunction of the heart in one or both twins.

Usually, twin-to-twin transfusion syndrome develops between week 16 to week 26 during the pregnancy period. It can be diagnosed during 10 to 14 weeks by measuring the amniotic fluid level through an ultrasound scan.

Usually, twin-to-twin transfusion syndrome develops between week 16 to week 26 during the pregnancy period. It can be diagnosed during 10 to 14 weeks by measuring the amniotic fluid level through an ultrasound scan.

The steps that are taken to avoid the effects of twin-to-twin transfusion are


- Laser Fetal Surgery - This laser fetal surgery targets the cause of twin-to-twin transfusion syndrome.


- Amnioreduction - In this procedure, the excess amount of amniotic fluid from the recipient twin is removed using a fine needle.

It is very difficult for doctors to diagnose twin-to-twin transfusion syndrome after the child's birth. Usually, twin-to-twin transfusion syndrome is diagnosed with the help of an ultrasound scan during weeks 16 and 26 of the pregnancy. It can also be diagnosed by measuring the amniotic fluid level.

Babies who are born with twin-to-twin transfusion syndrome can survive with a normal and healthy life. Almost 90 percent of these types of pregnancies can give a healthy life to at least one baby after leaving the hospital. In some countries, reports say both babies are living healthy lives.

A difference in size up to 20 percent between twins is considered normal. The difference in size may also reach up to 40 percent or above. Twenty percent is considered normal in monochorionic twins.

There are two criteria required for diagnosing the twin to twin transfusion syndrome.


- First is the presence of MCDA pregnancy, which is monochorionic diamniotic pregnancy.


- Second is the presence of polyhydramnios and oligohydramnios.

When assessing for fetal transfusion syndrome in a twin pregnancy, a percentage difference in body weight of approximately 20 % or more between the twins is considered significant. This significant weight discordance may indicate a higher likelihood of complications associated with twin-to-twin transfusion syndrome and warrant further evaluation and monitoring.

Twin-to-twin transfusion syndrome can resolve on its own in approximately 60 percent of babies with early twin-to-twin transfusion syndrome. It can also decide on its own if laser surgery should be performed.

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Dr. Veerabhadrudu Kuncham from iCliniq
Dr. Veerabhadrudu Kuncham

Pediatrics

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