Timing of Laser Photocoagulation for Twin-Twin Transfusion Syndrome

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) 4, 5
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, 2
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 6

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 3

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 3
The Society for Maternal-Fetal Medicine recommends an individualized approach to laser surgery for late-presenting TTTS (GRADE 1C) 3

Stage I TTTS (asymptomatic): Expectant management with at least weekly fetal surveillance is recommended, with over 75% of cases remaining stable or regressing without invasive intervention, and perinatal survival of about 86% 5, 6
Stage II-IV TTTS: Fetoscopic laser photocoagulation is the recommended treatment between 16 and 26 weeks, with a perinatal loss rate of 70-100% without therapy 4, 3
Even with laser treatment, there is still a 30-50% chance of perinatal mortality and 5-20% risk of long-term neurologic impairment 6

All patients with TTTS qualifying for laser therapy should be referred to a fetal intervention center for evaluation, consultation, and care 7
After laser therapy, weekly surveillance for 6 weeks is suggested, followed by resumption of every-other-week surveillance 8

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) 9
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 10