In brief — the direct answer
Twin-to-Twin Transfusion Syndrome (TTTS) is a rare and life-threatening condition that only affects identical twins sharing a single placenta (MCDA). It occurs when blood vessels on the placenta connect the two babies' circulations in an unbalanced way. One twin (the donor) pumps blood to the other (the recipient). Without intervention, the donor becomes anemic and small with no amniotic fluid, while the recipient becomes overloaded with blood, develops heart failure, and produces excessive amniotic fluid. At the MFM Unit, our fetal-therapy team assesses TTTS and discusses treatment options.
What is Twin-to-Twin Transfusion Syndrome (TTTS)?
TTTS is not a problem with the babies themselves, but a problem with the placental 'plumbing.'
- The Donor: Becomes dehydrated. Their kidneys stop producing urine, and they soon have no amniotic fluid (oligohydramnios), making them appear 'stuck' against the uterine wall.
- The Recipient: Receives too much blood. Their heart struggles to pump the extra volume, and they compensate by producing huge amounts of urine/amniotic fluid (polyhydramnios), which stretches the mother's uterus and causes discomfort.
Who is at risk?
TTTS only occurs in Monochorionic (shared-placenta) twins. It typically develops between 16 and 26 weeks of pregnancy. It is not caused by anything the mother did and cannot be prevented with diet or lifestyle changes; it is a technical event of placental development.
How we diagnose it
We use the Quintero Staging System to categorize severity:
- Stage I: Imbalance of fluid (excess in recipient, little in donor), but the donor's bladder is still visible.
- Stage II: The donor's bladder is no longer visible on ultrasound.
- Stage III: Abnormal Doppler blood flow in the brains or cords of either baby.
- Stage IV: The recipient twin shows signs of heart failure (hydrops).
- Stage V: Death of one or both twins.
What does management involve?
The definitive treatment for TTTS is Fetoscopic Laser Photocoagulation (FLPC):
- The Laser: A tiny camera (fetoscope) is inserted into the mother's uterus. We identify the connecting vessels on the placenta and use a laser to 'seal' them, separating the circulations.
- Amnioreduction: At the end of the surgery, we drain the excess fluid from the recipient’s sac to reduce the risk of premature labor.
- Success Rates: In expert hands, at least one baby survives in 85-90% of cases, and both babies survive in about 60-70% of cases.
What are the outcomes?
Outcome varies with stage, gestation, associated findings and response to treatment. Fetoscopic laser is established treatment for stage II–IV TTTS presenting at 16–26 weeks; stage I and presentations outside that window need individual assessment. Published survival estimates must not be represented as this unit’s audited results. Risks include membrane rupture, preterm birth, loss of one or both twins, recurrent TTTS, TAPS and neurological injury. Continued follow-up is essential even after technically successful surgery.
When to see a subspecialist
Suspected TTTS requires prompt assessment by a fetal-therapy centre. Bring the chorionicity report, fluid measurements, bladder findings and Doppler results if available. Referral should not wait for a later stage. Sudden abdominal enlargement, breathlessness, pain, contractions or reduced movements needs urgent maternity assessment.