Twin-to-Twin Transfusion Syndrome
Overview
Twin-to-Twin Transfusion Syndrome (TTTS) is a rare, serious condition that can occur in pregnancies where identical twins share a placenta, also known as monochorionic twins. This syndrome is characterized by an imbalance in the blood flow between the twins through connecting blood vessels in their shared placenta. This can lead to a disparity in the volume of blood and nutrients received by each twin, causing significant health risks.
Epidemiology
TTTS affects approximately 10-15% of monochorionic twin pregnancies. It typically develops during the second trimester, but can occur at any time during the pregnancy. The exact cause of TTTS is unknown, but it is believed to be related to the formation and distribution of blood vessels within the shared placenta.
Pathophysiology
In TTTS, abnormal blood vessel connections form in the shared placenta, allowing blood to flow unevenly between the twins. This results in one twin (the 'donor') transferring blood to the other twin (the 'recipient'). The donor twin may become anemic and have a lower amount of amniotic fluid, while the recipient twin may have too much blood, leading to heart complications and an excess of amniotic fluid.
Clinical Presentation
The clinical presentation of TTTS can vary greatly. The donor twin is often smaller, with a lower volume of amniotic fluid (oligohydramnios). The recipient twin is typically larger, with a higher volume of amniotic fluid (polyhydramnios). Both twins may show signs of heart complications. In severe cases, TTTS can lead to the death of one or both twins.
Diagnosis
TTTS is typically diagnosed through ultrasound during pregnancy. The ultrasound can reveal the presence of a shared placenta, the size difference between the twins, and the disparity in amniotic fluid volume. Further diagnostic tests may include Doppler ultrasonography to assess blood flow and echocardiography to evaluate heart function.
Treatment
The treatment for TTTS depends on the severity of the condition. Mild cases may be managed with close monitoring. More severe cases may require intervention, such as amnioreduction (removal of excess amniotic fluid), laser therapy to seal off the abnormal blood vessels, or in extreme cases, selective reduction.
Prognosis
The prognosis for TTTS varies depending on the severity of the condition and the timing and effectiveness of treatment. With early detection and appropriate treatment, the survival rate for at least one twin can be over 90%.