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Twin to Twin Transfusion Syndrome: What Is It?

Aug 03, 2023
pregnant mother sitting with doctor

Twin to Twin Transfusion Syndrome (TTTS) is a rare condition occurring in about 10-15% of twin or triplet pregnancies that share the placenta (monochorionic pregnancies). It occurs due to an imbalance in blood circulation between the twins, resulting in one baby transfusing a significant amount of blood to the other. As a consequence, the donor twin becomes smaller and has low amniotic fluid, while the recipient twin grows well but experiences cardiac overload and excess amniotic fluid (polyhydramnios). If left untreated, TTTS can lead to the loss of affected fetuses.

What Causes Twin-to-Twin Transfusion Syndrome?

The exact cause of TTTS is not fully understood, but it is believed to be linked to abnormal vascular connections (anastomoses) in the shared placenta. These anastomoses are responsible for balancing blood flow between the twins. TTTS occurs when these connections are insufficient, leading to a net flow of blood from one twin to the other.

TTTS Symptoms, Diagnosis and Treatment

In its early stages, TTTS is completely asymptomatic for the mother because it typically occurs early in the pregnancy (most often between 16-26 weeks). That's why it is essential for all pregnant women to have an ultrasound in the first trimester to identify multiple pregnancies and verify if the fetuses share the placenta. In such cases, close monitoring is recommended from 16 weeks onwards to identify significant differences in the amounts of amniotic fluid and the growth of both fetuses, which could indicate a potential complication.

TTTS is categorized into stages I to V based on the severity of the condition. Stage I is defined by a significant discrepancy in amniotic fluid while the bladder is still visible in the donor twin. Stage II is when the donor twin’s bladder is no longer visible, while Stage III is characterized by severe abnormalities of the blood flow of one or both twins, suggesting early stages of heart failure. Stage IV involves signs of too much fluid leaving the baby’s bloodstream (a life-threatening condition called hydrops), and Stage V sadly consists of intrauterine fetal demise in one or both of the fetuses.

Luckily, about 55-70% of pregnancies at Stage I remain stable throughout pregnancy or actually even remit spontaneously. Proper tracking and management of TTTS is incredibly important, and while many fetal centers offer conservative management, the North American Fetal Therapy Network (NAFTNet) states that only a minimally invasive procedure called fetoscopic laser coagulation (FLC) is able to protect against double fetal loss or extreme preterm delivery before 26 weeks.

anterior view of twin to twin transfusion syndrome

FLC is considered the gold standard of treatment for severe stage II-IV cases between 17 and 26 weeks; most healthcare centers with a high volume of cases can achieve a good double survival rate of around 70% and an even higher survival rate in at least one twin (90%). Parents should be aware of shortening of the cervix, maternal discomfort and severe progressive polyhydramnios, which are mostly taken as signs for immediate laser intervention.

Average delivery after intervention ranges from 31-36 weeks, though the best timing for a preterm delivery has yet to be determined. Working closely with our provider team to make this decision based on ultrasound findings, assessment from experts and parental choices is the best-case scenario.

How the Fetal Center at Nationwide Children’s Hospital Can Help

Nationwide Children's Hospital Fetal Center offers comprehensive care for TTTS, with a team of professionals from different specialties experienced in handling such cases. They aim to provide the best-informed decisions, early identification, and appropriate care management plans to support families through this challenging journey. The hospital's focus on family-centered care, advanced treatment, and proper education and counseling make it a preferred choice for managing TTTS.

Receiving a TTTS diagnosis can be overwhelming, but with Nationwide Children's Hospital's expertise and support, families can navigate this difficult situation with confidence and care.

Fetal Center at Nationwide Children's Hospital
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Featured Expert

Adolfo Etchegaray
Adolfo Etchegaray, MD
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Adolfo Etchegaray, MD, is the Chief of Fetal Medicine at Nationwide Children’s Hospital. He brings over a decade of experience in maternal-fetal medicine and fetal surgery and years of program development to our Fetal Center.

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Oluseyi Ogunleye
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700 Children’s® features the most current pediatric health care information and research from our pediatric experts – physicians and specialists who have seen it all. Many of them are parents and bring a special understanding to what our patients and families experience. If you have a child – or care for a child – 700 Children’s was created especially for you.