Fetofetal transfusion

Fetofetal Transfusion Syndrome (FFTS), also known as Twin-to-Twin Transfusion Syndrome (TTTS), is a prenatal condition that affects monozygotic twins (identical twins) who share a single placenta (monochorionic twins). This syndrome occurs when there is an imbalance in the blood flow between the twin fetuses through vascular connections in the shared placenta. One twin, referred to as the donor twin, receives less blood and the other, known as the recipient twin, receives too much.

Causes and Pathophysiology

Fetofetal transfusion syndrome is caused by abnormal blood vessel connections in the placenta that allow blood to flow unevenly between the twins. The exact cause of these abnormal connections is not fully understood, but they are inherent to the development of the shared placenta in monozygotic twin pregnancies. The donor twin may suffer from hypovolemia, anemia, and growth restriction due to reduced blood supply, while the recipient twin may experience hypervolemia, polycythemia, and an increased risk of cardiac failure due to the excess blood volume.

Symptoms and Diagnosis

Symptoms of FFTS can vary depending on the severity of the condition but may include a noticeable difference in amniotic fluid levels between the twins, with the donor twin having reduced amniotic fluid (oligohydramnios) and the recipient twin having increased amniotic fluid (polyhydramnios). Ultrasound is the primary tool for diagnosing FFTS, allowing for the assessment of amniotic fluid levels, bladder size in both fetuses, and blood flow through the placental connections.

Staging

The severity of fetofetal transfusion syndrome is often classified according to the Quintero staging system, which ranges from Stage I (mild) to Stage V (critical). This system considers factors such as amniotic fluid discrepancies, bladder visibility, abnormal Doppler studies, and fetal hydrops.

Treatment

Treatment options for FFTS depend on the severity of the condition and the gestational age at diagnosis. Interventions may include:

- Amnioreduction: Removal of excess amniotic fluid to reduce the risk of preterm labor and improve the imbalance in blood flow. - Laser Photocoagulation: A minimally invasive procedure that uses laser energy to seal off the abnormal vascular connections in the placenta. - Selective Fetoscopic Laser Photocoagulation (SFLP): A more targeted approach to laser therapy that aims to preserve the health of both twins by selectively treating the problematic vessels. - Cord Occlusion: In severe cases, this procedure may be considered to save one twin if the survival of both is not possible.

Prognosis

The prognosis for fetofetal transfusion syndrome varies widely and depends on the stage at diagnosis, the timeliness, and the type of intervention. Early detection and treatment can significantly improve outcomes for both twins. However, the condition can lead to complications such as preterm labor, neurological damage, and, in severe cases, the death of one or both twins.

Prevention

Currently, there are no known methods to prevent fetofetal transfusion syndrome. Regular prenatal care and monitoring are crucial for early detection and management of this condition in pregnancies identified as high-risk due to the presence of monochorionic twins.