Twin-to-Twin Transfusion Syndrome

Twin-to-twin transfusion syndrome (TTTS) complicates 10 to 15% of monochorionic diamniotic twin pregnancies, resulting from unbalanced net blood flow across placental vascular anastomoses (arteriovenous anastomoses), causing a donor twin (hypovolaemic, oliguric, oligohydramnios, growth restricted) and a recipient twin (hypervolaemic, polyuric, polyhydramnios, heart failure). Without treatment, perinatal mortality exceeds 90% for severe disease presenting before 26 weeks.

Quintero staging:

• Stage I: oligohydramnios (maximum vertical pocket under 2 cm) in the donor and polyhydramnios (above 8 cm before 20 weeks; above 10 cm after 20 weeks) in the recipient, bladder visible in donor
• Stage II: donor bladder not visible
• Stage III: critically abnormal Doppler (absent or reversed end diastolic flow in the umbilical artery, reversed a-wave in the ductus venosus, or pulsatile umbilical vein flow)
• Stage IV: hydrops in one or both twins
• Stage V: demise of one or both twins

• Rapid uterine enlargement, abdominal pain or tightness, preterm contractions, maternal dyspnoea
• Mother may develop mirror syndrome, polyhydramnios complications, and preterm labour
• Fetal: discordant amniotic fluid volumes ("stuck twin" appearance with the donor adherent to the uterine wall), size discordance (not required for diagnosis), recipient cardiomyopathy (tricuspid regurgitation, ventricular hypertrophy), and neurological injury risk
• Postnatal: donor anaemic, recipient polycythaemic; complications of prematurity, neurological impairment (in 10 to 20%), cardiac and renal sequelae

• Diagnosis by ultrasound: monochorionic diamniotic twins with polyhydramnios and oligohydramnios sequence
• Chorionicity must be established before 14 weeks (T sign for monochorionic, lambda sign for dichorionic)
• Surveillance of monochorionic twins: ultrasound every 2 weeks from 16 weeks to 26 weeks (fluid volumes, bladder, Doppler), then every 2 to 4 weeks
• Fetal echocardiography for the recipient (Cincinnati score, myocardial performance index)
• Differential diagnosis: selective fetal growth restriction, PPROM of one twin, discordant anomalies

• Stage I: close surveillance (ultrasound weekly to fortnightly); about 60 to 70% remain stable or regress.
• Stage II to IV (or progressing stage I, or symptomatic mother) between 16 and 26 weeks: fetoscopic laser photocoagulation of placental vascular anastomoses (Solomon technique: coagulation of the vascular equator to reduce recurrence), performed under local or regional anaesthesia at a fetal medicine centre.
  • Survival of at least one twin about 85 to 90%, both twins about 60 to 70%; neurological impairment about 5 to 10%.
  • Complications: PPROM (about 10 to 20%), preterm birth (average delivery at about 32 weeks), recurrent TTTS and twin anaemia polycythaemia sequence (TAPS, about 5 to 15%), and amniotic band formation.
  • Give prophylactic antibiotics (cefazolin 1 to 2 g) and tocolysis (indomethacin 50 mg) perioperatively; some centres use nifedipine.
• After 26 weeks: serial amnioreduction (to remove up to 3 L at a time), selective feticide (radiofrequency ablation or cord occlusion) in cases of one twin with severe anomaly or failed laser, or delivery.
• Follow up:
  • Ultrasound weekly for 2 weeks after laser, then fortnightly.
  • Doppler for TAPS (middle cerebral artery peak systolic velocity).
  • Corticosteroids at 24 to 34 weeks (betamethasone 12 mg IM, two doses).
  • Delivery at 34 to 36 weeks (earlier for complications) by caesarean or vaginal delivery according to presentation.
• Neonatal care: neonatal ICU, cranial ultrasound, and developmental follow up to 2 years.