Twin-to-twin transfusion syndrome occurs only in monochorionic pregnancies, where fetuses share a placenta. Abnormal vascular connections can create an unbalanced circulation, producing low fluid and reduced bladder filling in the donor and high fluid with cardiovascular strain in the recipient.
Assessment before laser
The team confirms chorionicity, gestational age, deepest fluid pockets, bladder visibility, Doppler findings, growth, fetal anatomy, cardiac function, cervical length, placental position, and the stage and evolution of disease. TAPS, selective fetal growth restriction, structural abnormality, membrane separation, or threatened preterm birth may alter the plan.
What laser aims to do
During fetoscopy, the placental vascular equator is inspected and communicating vessels are coagulated with laser. The aim is to separate the shared circulation rather than simply remove excess amniotic fluid. Technique and access are tailored to placental anatomy.
What counselling should cover
Laser does not guarantee survival of one or both fetuses. Potential complications include fluid leakage, membrane rupture, bleeding, infection, preterm birth, pregnancy loss, recurrent or persistent TTTS, post-laser TAPS, fetal neurological injury, and technical inability to complete treatment. The alternatives may include surveillance, amnioreduction in selected circumstances, another fetal procedure, or delivery depending on gestation and disease.
Follow-up remains intensive
Ultrasound after laser reassesses fetal heart activity, fluid, bladders, Doppler, growth, cervix, and evidence of recurrent haemodynamic imbalance. Longer-term planning includes fetal brain assessment when indicated, timing and place of delivery, neonatal review, and developmental follow-up.
Suspected TTTS should be referred promptly because staging and the treatment window are time-sensitive. The dated programme-status panel gives the current TTTS-laser pathway classification; intervention remains subject to specialist confirmation, technical candidacy, governance, and informed consent.
The essential distinctions
One placenta changes how twins are monitored.
Twins may share a placenta while having separate amniotic sacs. Placental connections can allow blood to flow between the babies.
- Shared placental vessels
TTTS and TAPS arise from particular patterns of shared circulation. They are different conditions.
- Separate fluid spaces
Fluid around each baby is assessed alongside bladders, growth, and Doppler.
- Two individual assessments
The size of one baby alone cannot diagnose a transfusion syndrome.
Visual decision pathway
TTTS laser: mechanism-led pathway
The decision moves from shared-placenta diagnosis to staging, procedural feasibility and intensive post-laser surveillance.
- ConfirmProve monochorionic TTTS
Chorionicity, fluid pattern, bladders, Doppler, growth and cardiac assessment.
- StageDefine disease and competing risks
Gestation, progression, cervix, membranes, anatomy, TAPS and selective restriction.
- MapAssess fetoscopic access
Placental position, vascular equator, maternal factors and technical completion risk.
- SeparateLaser communicating vessels
Treat the shared placental mechanism, with agreed alternatives if completion is impossible.
- WatchContinue intensive follow-up
Survival, fluid, Doppler, TAPS, brain assessment, growth, cervix and delivery planning.