What are the risks, management, and treatment options for a patient with twin-to-twin transfusion syndrome (TTS) in a monochorionic diamniotic (MCDA) twin pregnancy, characterized by polyhydramnios and oligohydramnios?

Management of Twin-to-Twin Transfusion Syndrome (TTTS) in Monochorionic Diamniotic Twin Pregnancy

Fetoscopic laser photocoagulation is the recommended treatment for stage II-IV TTTS presenting between 16-26 weeks of gestation to optimize fetal survival and reduce neurological morbidity. 1

Diagnosis and Staging

TTTS is diagnosed by ultrasound based on two essential criteria:

• Presence of monochorionic diamniotic (MCDA) placentation (identified by T-sign)
• Oligohydramnios in the donor twin (maximal vertical pocket [MVP] ≤2 cm) and polyhydramnios in the recipient twin (MVP ≥8 cm) 1

The Quintero staging system is used to classify TTTS severity:

• Stage I: Oligohydramnios/polyhydramnios sequence only
• Stage II: Non-visualization of donor twin bladder
• Stage III: Abnormal Doppler studies (umbilical artery, ductus venosus, or umbilical vein)
• Stage IV: Presence of hydrops fetalis
• Stage V: Demise of one or both twins 1

Counseling for Mrs. Wong

General MCDA Twin Pregnancy Risks

1. Higher complication rate: MCDA twins affect 8-10% of twin pregnancies and have higher risks than dichorionic twins 1
2. Maternal risks: Increased risk of preeclampsia, gestational diabetes, and need for intervention 1
3. Pregnancy monitoring: Requires consultant-led care with more frequent antenatal visits

Specific TTTS Counseling

1. Disease prevalence: TTTS complicates 8-12% of MCDA twin pregnancies 1
2. Disease mechanism: Imbalanced blood flow through placental anastomoses causing volume discrepancy between twins 2
3. Prognosis: Varies by stage - Stage I has 86% survival with expectant management, while advanced stages have 70-100% mortality without intervention 1
4. Cardiovascular complications: Recipient twin at risk for cardiac hypertrophy and dysfunction; donor twin at risk for growth restriction 2
5. Long-term outcomes: Even with treatment, 5-20% risk of neurological impairment in survivors 1

Management Plan

Surveillance

• Serial ultrasound evaluations every 2 weeks starting at 16 weeks until delivery 1
• Monitoring should include:
  • Amniotic fluid volumes in both sacs
  • Bladder filling assessment
  • Doppler studies of umbilical arteries
  • Middle cerebral artery Doppler when indicated 1
• Fetal echocardiography for both twins due to increased risk of cardiac abnormalities 1

Treatment Options Based on Stage

1. Stage I TTTS:

   • Often managed expectantly as >75% remain stable or regress without intervention 1
   • Close monitoring every 1-2 weeks

2. Stage II-IV TTTS (16-26 weeks):

   • Fetoscopic laser photocoagulation of placental anastomoses is the standard treatment 1
   • Outcomes: 50-70% dual survival, 20-30% single survival, 10-20% no survivors 1

3. Advanced TTTS or >26 weeks:

   • Serial amnioreduction may be considered
   • Early delivery if >28 weeks with mature lungs 1

4. Other options:

   • Selective reduction in cases with severe anomalies or discordant growth
   • Pregnancy termination in severe early cases 1

Post-Treatment Management

• Administer corticosteroids for fetal lung maturation between 24-34 weeks 1
• Continue regular ultrasound surveillance after treatment
• Plan for delivery at 34-36 weeks even after successful treatment 1

Potential Complications

1. Fetal complications:

   • Intrauterine growth restriction
   • Cardiac dysfunction (particularly in recipient twin)
   • Neurological injury
   • Intrauterine fetal demise 2

2. Treatment-related complications:

   • Premature rupture of membranes
   • Preterm labor
   • Placental abruption
   • Procedure-related fetal loss 1

3. Long-term complications:

   • Neurological impairment in 5-20% of survivors even with laser treatment 1
   • Developmental delays
   • Cerebral palsy

Key Points for Clinical Practice

• Early diagnosis through regular ultrasound surveillance is crucial for optimal outcomes
• The presence of arterioarterial anastomoses may reduce risk of TTTS progression 3
• Even with isolated polyhydramnios in one twin without oligohydramnios in the other, close monitoring is warranted as 23.4% may progress to TTTS 3
• Fetoscopic laser surgery addresses the underlying pathophysiology and provides better outcomes than amnioreduction 4
• Coordination between maternal-fetal medicine specialists and neonatology is essential for optimal care