Summary about Disease
Twin-to-twin transfusion syndrome (TTTS) is a rare but serious complication of monochorionic twin pregnancies. This means the twins share a single placenta. In TTTS, abnormal blood vessel connections within the placenta allow blood to flow disproportionately from one twin (the donor) to the other (the recipient). The donor twin loses blood and can become anemic and dehydrated. The recipient twin receives too much blood, leading to increased amniotic fluid (polyhydramnios), heart strain, and other complications. If left untreated, TTTS can be life-threatening for both twins.
Symptoms
Symptoms of TTTS can vary depending on the severity and stage of the condition. Some common signs include:
Rapid growth of the uterus: The mother's abdomen may grow faster than expected for the gestational age due to polyhydramnios in the recipient twin's amniotic sac.
Discomfort or tightness in the abdomen: Caused by the excessive amniotic fluid.
Premature contractions: The overdistended uterus can trigger premature labor.
Decreased fetal movement: The donor twin may show reduced activity due to decreased blood volume and amniotic fluid.
Visible size difference between twins on ultrasound: As the condition progresses.
Recipient twin has excess amniotic fluid (polyhydramnios): Defined as a single deepest vertical pocket (SDP) of amniotic fluid ≥ 8 cm.
Donor twin has little to no amniotic fluid (oligohydramnios): Defined as a single deepest vertical pocket (SDP) of amniotic fluid ≤ 2 cm.
Causes
The exact cause of TTTS is not fully understood, but it is related to abnormal blood vessel connections (anastomoses) in the shared placenta of monochorionic twins. These connections allow blood to flow between the twins. In TTTS, the blood flow becomes unbalanced, with one twin donating more blood than it receives, and the other twin receiving an excessive amount. The underlying factors that lead to the development of these abnormal connections are still being researched.
Medicine Used
There isn't a direct "medicine" to cure TTTS. Instead, treatments aim to manage the complications caused by the unbalanced blood flow.
Amnioreduction: A procedure to drain excess amniotic fluid from the recipient twin's sac. This provides temporary relief but does not address the underlying problem.
Laser Ablation of Anastomosing Vessels: This is the primary treatment. Fetoscopic laser ablation involves using a laser to seal off the abnormal blood vessel connections on the surface of the placenta, effectively separating the circulations of the two twins.
Selective Feticide: In severe cases where one twin has a very poor prognosis or is already deceased, selective feticide (termination of one twin) may be considered to improve the chances of survival for the remaining twin. This is a very difficult decision and is reserved for extreme situations.
Septostomy: Creating a hole in the dividing membrane between the amniotic sacs to equalize pressures. This is generally not recommended as the primary treatment.
Is Communicable
No, twin-to-twin transfusion syndrome is not communicable. It is a complication that arises due to specific placental blood vessel arrangements in monochorionic twin pregnancies. It is not caused by any infectious agent and cannot be transmitted from person to person.
Precautions
There are no known precautions a woman can take before or during pregnancy to prevent TTTS from occurring. TTTS is a random event related to the formation of the shared placenta in monochorionic twins. However, early and regular monitoring is crucial for monochorionic twin pregnancies to detect TTTS as early as possible.
Early and frequent ultrasounds: Monochorionic twin pregnancies require serial ultrasounds, typically every 1-2 weeks, starting around 16 weeks of gestation, to monitor for signs of TTTS.
Expert Consultation: Referral to a maternal-fetal medicine specialist (MFM) experienced in managing TTTS is important if any signs of the condition are suspected.
How long does an outbreak last?
TTTS is not an "outbreak" in the traditional sense of an infectious disease. Rather, it develops over time during pregnancy. The progression of TTTS can vary greatly. In some cases, it may develop rapidly over a few days or weeks. In other cases, it may progress more slowly. Without treatment, TTTS can continue to worsen throughout the pregnancy, leading to significant complications. Treatment is aimed at stopping the progression of the disease.
How is it diagnosed?
TTTS is primarily diagnosed through ultrasound examination. Key diagnostic criteria include:
Monochorionic diamniotic (MCDA) twin pregnancy confirmed by ultrasound. This means the twins share a single placenta but have separate amniotic sacs.
Polyhydramnios in the recipient twin's sac: Defined as a single deepest vertical pocket (SDP) of amniotic fluid ≥ 8 cm.
Oligohydramnios in the donor twin's sac: Defined as a single deepest vertical pocket (SDP) of amniotic fluid ≤ 2 cm. The donor twin's bladder may not be visible.
Discordant fetal size: A significant difference in size between the two twins may be observed as the condition progresses.
Doppler studies: Blood flow studies can also reveal abnormalities in the blood flow patterns between the twins.
Quintero Staging System: This system is used to classify the severity of TTTS, guiding treatment decisions.
Timeline of Symptoms
The timeline of symptoms can vary significantly, but here's a general idea:
16-26 weeks: This is the most common period for TTTS to develop. Routine ultrasounds during this time may detect early signs.
Early Stages: Rapid uterine growth, abdominal discomfort, and subtle changes in fetal movement might be the first noticeable signs.
Progression: As TTTS progresses, the polyhydramnios and oligohydramnios become more pronounced, leading to more significant symptoms for the mother (e.g., contractions, difficulty breathing). The size difference between the twins becomes more apparent on ultrasound.
Late Stages (Untreated): In the absence of treatment, the condition can lead to premature labor and delivery, heart failure in the recipient twin, and potentially fetal demise of one or both twins.
Important Considerations
Early Detection is Key: The earlier TTTS is diagnosed and treated, the better the chances of survival and a positive outcome for both twins.
Specialized Care is Essential: Management of TTTS requires the expertise of a maternal-fetal medicine specialist (MFM) and a center experienced in performing fetoscopic laser ablation.
Emotional Support: Dealing with a TTTS diagnosis can be emotionally challenging. Support groups and counseling can be helpful for the parents.
Long-Term Follow-Up: Even after successful treatment, long-term follow-up of the twins is important to monitor for any potential complications.
Recurrence Risk: While rare, there is a slightly increased risk of TTTS in subsequent monochorionic twin pregnancies.