At what gestational age can laser photocoagulation (laser treatment) be performed for twin-to-twin transfusion syndrome (TTTS)?

Timing of Laser Photocoagulation for Twin-Twin Transfusion Syndrome

Fetoscopic laser photocoagulation for twin-twin transfusion syndrome (TTTS) is typically performed between 16 and 26 weeks of gestation, but can be considered as early as before 16 weeks with an individualized approach for early-presenting cases. 1

Standard Timing for Laser Therapy

• Fetoscopic laser photocoagulation is recommended as the standard treatment for stage II through stage IV TTTS presenting between 16 and 26 weeks of gestation (GRADE 1A) 1
• Ultrasound surveillance for TTTS should begin at 16 weeks of gestation for all monochorionic-diamniotic twin pregnancies and continue at least every 2 weeks until delivery 1
• The diagnosis of TTTS requires two criteria: (1) the presence of a monochorionic diamniotic pregnancy; and (2) the presence of oligohydramnios (maximal vertical pocket ≤2 cm) in one sac and polyhydramnios (maximal vertical pocket ≥8 cm) in the other sac 1

Early Laser Therapy (Before 16 Weeks)

• Early laser surgery (before 17 weeks) has shown similar survival rates and gestational age at delivery compared to procedures performed between 17 and 26 weeks 1
• However, early laser procedures are associated with higher complication rates:
  • Significantly higher rates of chorioamniotic separation (34.3% vs 1.3%) 2
  • Higher rates of preterm prelabor rupture of membranes (45.7% vs 25.0%) 2
  • Higher rates of chorioamnionitis (11.4% vs 1.3%) 2
• Despite these complications, twin survival does not appear to be negatively impacted following early laser surgery 2

Late Laser Therapy (After 26 Weeks)

• For TTTS presenting beyond 26 weeks, laser surgery may be considered for select cases of severe disease presenting up to the very early third trimester 1
• Small studies comparing laser surgery performed between 26 and 28 weeks with procedures at standard gestational ages showed no differences in operative time, surgical complications, gestational age at delivery, or survival of at least one neonate 1
• The Society for Maternal-Fetal Medicine recommends an individualized approach to laser surgery for late-presenting TTTS (GRADE 1C) 1

Management Based on TTTS Stage

• Stage I TTTS (asymptomatic): Expectant management with at least weekly fetal surveillance is recommended 1, 3

  • Over 75% of stage I TTTS cases remain stable or regress without invasive intervention, with perinatal survival of about 86% 1
  • In a randomized trial, 41% of expectantly managed stage I cases remained stable with 86% dual intact survival at 6 months 3
  • Consider laser therapy for stage I TTTS between 16 and 26 weeks only if complicated by maternal polyhydramnios-associated symptoms 1

• Stage II-IV TTTS: Fetoscopic laser photocoagulation is the recommended treatment between 16 and 26 weeks 1, 4

  • Without therapy, advanced-stage TTTS has a perinatal loss rate of 70-100% 1
  • Even with laser treatment, there is still a 30-50% chance of perinatal mortality and 5-20% risk of long-term neurologic impairment 1, 4

Important Considerations

• All patients with TTTS qualifying for laser therapy should be referred to a fetal intervention center for evaluation, consultation, and care 1
• After laser therapy, weekly surveillance for 6 weeks is suggested, followed by resumption of every-other-week surveillance 1
• Fetoscopic laser photocoagulation is the only therapy that directly addresses the underlying pathophysiology of TTTS by ablating placental vascular anastomoses 4, 5
• The Solomon technique (selective coagulation to connect the anastomoses ablation sites) has been introduced to reduce residual anastomoses 4

Delivery Timing After Treatment

• Following resolution of TTTS after fetoscopic laser surgery, delivery of dual-surviving monochorionic-diamniotic twins is recommended at 34 to 36 weeks of gestation (without other indications for earlier delivery) 1
• In TTTS pregnancies complicated by posttreatment single fetal demise, full-term delivery (39 weeks) of the surviving co-twin is recommended unless indications for earlier delivery exist 1