Twin-to-twin transfusion syndrome

Disease Description (Causes and Symptoms)

• Definition: Twin-to-Twin Transfusion Syndrome (TTTS) is a condition that occurs in monozygotic twins sharing a single chorion (in which all blood vessels may be connected), where blood flow continuously shifts from one fetus (the donor) to the other (the recipient) due to vascular anastomoses within the placenta.
• Causes and pathophysiology: Blood flow moves asymmetrically due to arterio-venous anastomoses in the placenta. The donor fetus may show anemia, oliguria, growth restriction, and oligohydramnios due to reduced blood volume, while the recipient fetus may show cardiac strain and heart failure, polycythemia, polyhydramnios, and hydrops due to excessive blood flow.
• Main symptoms (prenatal findings): Imbalance in amniotic fluid volume (polyhydramnios on one side and reduced amniotic fluid on the other), weight imbalance between the fetuses, abnormal heart sounds and cardiac dysfunction, and changes in the vitality of both fetuses. As postpartum diagnostic supplementary indicators, a weight difference of ≥20% or a difference in venous blood hemoglobin of ≥5 g/dL may be used.
• Diagnostic support: Severity is classified using clinical indicators such as prenatal ultrasonography (amniotic fluid measurements, fetal growth, cardiac findings) and Quintero staging (Stages 1–5).

Treatment Methods and Precautions

• Standard and definitive treatment
  • Fetoscopic laser photocoagulation / selective laser coagulation: Definitive correction by selectively coagulating the vascular connections in the placenta. It can generally be performed between 15 and 26 weeks of gestation and is considered the standard treatment for severe TTTS.
• Supportive and alternative treatments
  • Repeated amnioreduction: Periodically reducing excess amniotic fluid in the recipient fetus to help relieve maternal symptoms and prevent preterm labor. It is not a definitive treatment.
  • Selective feticide: Considered when the viability and prognosis of one of the two fetuses are extremely poor.
  • Other treatments: Limited applications such as septostomy.
• Prenatal and major treatment-related care
  • Antibiotic/drug treatment: There is no specific standard drug treatment. In cases of fetal anemia, fetal transfusion may be considered if necessary.
  • Steroids: Administered to promote fetal lung maturation when the risk of preterm birth is high or early delivery is possible.
• Complications and treatment risks
  • Complications of laser treatment: PPROM (preterm premature rupture of membranes), preterm labor, bleeding, and possible fetal injury.
  • Poor prognosis if untreated: The perinatal mortality rate is very high in high-risk groups (60–90% according to the literature).
• Follow-up and lifestyle management
  • Frequent ultrasound follow-up (every 1–2 weeks or according to the stage) and intensified monitoring.
  • If symptoms such as shortness of breath, abdominal distension, or vaginal bleeding occur, visit a hospital immediately.
  • Daily activity restrictions depend on the individual situation (the doctor will decide whether to recommend activity restriction or rest).

Outpatient Visit Checkpoints (Preparation and Examples of Questions)

• Recommended items to bring
  • Recent prenatal ultrasound records (findings and images) and previous ultrasound results
  • List of currently used medications and supplements
  • Previous obstetric history (gestational age, whether assisted reproductive technology was used, and previous delivery history)
  • Record of recent symptoms (changes in fetal movement, abdominal distension/shortness of breath, etc.), last menstrual period, and confirmed gestational age
  • Laboratory and test results (if available)
• Materials to show the doctor during the outpatient visit
  • Difference in amniotic fluid volume (AFI or MVP values), fetal echocardiography results, and fetal weight trend chart
• Examples of questions to organize in advance
  • When the symptoms began and how they have changed (for example, whether abdominal distension suddenly became more severe)
  • Whether ART (assisted reproductive technology) was previously used
  • Family history (unusual or relevant conditions)

Examples of General Questions to Ask the Doctor

• What is the severity of this condition (Quintero stage), and what treatment options are currently recommended?
• What are the success rates and expected complications of laser coagulation (or amnioreduction)?
• When should the procedure be performed (at what gestational age), and what is the expected schedule for hospitalization and follow-up tests after the procedure?
• What are the expected short- and long-term prognoses for the fetuses (neonatal survival rate and risk of neurodevelopmental problems)?
• What risks or precautions affect the mother?

Examples of Condition-Specific Questions

• Based on the current ultrasound findings (amniotic fluid volume, fetal cardiac function, and growth indicators), what is the Quintero stage, and what treatment is recommended accordingly?
• What is the expected success rate of laser coagulation (the survival rate for each twin), and what are the risks of PPROM and preterm delivery after the procedure?