Multiple Pregnancy · TTTS
TTTS — Twin-Twin Transfusion Syndrome
Serious complication of identical twins sharing a placenta. Quintero staging I-V. Fetoscopic laser surgery is first-line for stages II-IV (~85% one twin survives; ~70% both). UK fetal medicine specialist centres.
Last reviewed 2 June 2026
TTTS Quintero staging
Monochorionic twin pregnancy
Quintero stage
Not TTTS — polyhydramnios/oligohydramnios criteria not met
Not TTTS — continue routine monochorionic surveillance (q2-weekly scans from 16 wk).
Troubleshooting + common pitfalls
- Misdiagnosing TTTS in dichorionic twins. Quintero criteria apply ONLY to monochorionic-diamniotic twins (shared placenta with vascular anastomoses). Selective FGR in dichorionic twins is a different entity. Establish chorionicity at 11–14 wk (lambda sign = dichorionic; T sign = monochorionic).
- Confusing TTTS with selective FGR (sFGR). In sFGR (MC twins), there’s a size discordance but the smaller twin’s amniotic fluid is normal or mildly reduced — not the “stuck twin” pattern of TTTS oligohydramnios. The poly/oligo sequence is required for TTTS diagnosis.
- Confusing TTTS with TAPS (Twin Anemia-Polycythaemia Sequence). TAPS is a chronic, low-volume net transfer producing Hb discordance without the poly/oligo sequence. Diagnosed by MCA-PSV (donor > 1.5 MoM, recipient < 1.0 MoM) and Hb difference at birth. Distinct natural history and management.
- Stage I observation in a deteriorating fetus. ~15–20 % of Stage I cases progress; some centres offer laser at Stage I in particular contexts (short cervix, large EFW discordance). The decision needs explicit MFM + family discussion; default observation isn’t always best.
- Late presentation > 26 wk. Laser ablation is technically more difficult and less effective. Amnioreduction may give symptomatic relief and modest GA gain; otherwise delivery weighed against prematurity.
- Single demise in MC twins. Surviving co-twin has ~20–30 % risk of neurological injury from acute transfusion at the moment of demise. Urgent MRI brain at 4–6 wk and at term/birth.
- Cervix in TTTS. Polyhydramnios stretches the uterus and shortens the cervix; preterm labour is a common indirect cause of poor outcomes. Serial CL surveillance + low threshold for cerclage/pessary if < 25 mm.
- Wrong CTG / Doppler twin labelled. Donor vs recipient labelling must be CONSISTENT across scans. Use stable anatomical references (left/right of mother, anterior/posterior placental cord insertion).
- Antenatal steroids in TTTS. Pre-treat with ANS before laser at ≥ 23 wk in case of preterm delivery; certainly before delivery at < 34 wk.
Educational tool only — not medical advice. Quintero 1999 J Perinatol; SMFM Consult #56 2020; Solomon trial Lancet 2014. TTTS is managed by specialised fetal-medicine teams.
What does this mean?
TTTS complicates ~10–15 % of monochorionic- diamniotic twin pregnancies. It is caused by unbalanced inter-twin transfusion across placental vascular anastomoses — the donor twin becomes hypovolaemic, anuric, and oligohydramniotic (the “stuck twin”); the recipient becomes hypervolaemic, polyhydramniotic, and may develop hydrops and cardiac failure. Without treatment, mortality is ~80–90 % at advanced stages. The Solomon trial (Lancet 2014) established fetoscopic laser ablation of placental anastomoses as the first-line treatment at Quintero II–IV between 16–26 weeks, with survival of at least one twin ~85 % and both twins ~65 %. Two recurring decision points: (1) Stage I observation vs intervention — 75 % stabilise but 15–20 % progress; cervix shortening, large EFW discordance, or rapid progression tip toward earlier intervention. (2) Single co-twin demise — the survivor faces ~20–30 % neurological injury risk from acute transfusion at the moment of demise; MRI surveillance is mandatory. Differentials to keep straight: selective FGR (sFGR) shares monochorionic context but lacks the poly/oligo sequence; TAPS is the chronic low-volume cousin diagnosed by MCA-PSV discordance, not amniotic fluid.
What is TTTS?
Complication of monochorionic-diamniotic (MC-DA) identical twins sharing a placenta. Blood vessels connect the twins; flow becomes unequal — one twin (donor) loses blood; the other (recipient) gets too much.
Affects ~10-15% of MC twins. Emergency without treatment — high mortality.
How it’s diagnosed
MC twin ultrasound surveillance from 16 weeks. Key signs:
- Major amniotic fluid discrepancy (donor <2 cm; recipient >8 cm).
- Bladder visibility (donor not visible; recipient distended).
- Doppler changes.
- Growth discrepancy.
Quintero staging
- I: oligo/polyhydramnios; BOTH bladders visible; Doppler normal.
- II: donor bladder NOT visible.
- III: ABNORMAL Dopplers.
- IV: hydrops in one / both twins.
- V: one or both twins dead.
Treatment
- Stage I: observation or intervention depending on centre.
- Stages II-IV: fetoscopic laser coagulation first-line.
- Amnioreduction sometimes if laser unavailable; less effective.
- Planned delivery 32-36 weeks after laser.
Laser surgery
- Spinal / local anaesthetic.
- Fetoscope through mum’s abdomen.
- Placental vessel connections between twins lasered.
- 30-60 min usually.
- Sometimes amnioreduction at end.
- Usually next-day discharge; close follow-up.
Risks of laser
- Miscarriage / preterm labour: 5-10% within 7 days.
- PPROM: 10-30%.
- TAPS (twin anaemia polycythaemia sequence): ~5% post-laser.
- Recurrent TTTS: ~5%.
Risks balanced against untreated TTTS mortality (~80-100% Stage III-IV).
UK fetal medicine centres
- Guy’s + St Thomas’ / King’s College (London).
- UCL (London).
- University Hospital Birmingham.
- Royal Victoria Infirmary (Newcastle).
- St Mary’s (Manchester).
- Other tertiary centres.
Prognosis with laser
- ~85% at least one twin survives.
- ~70% both twins.
- ~10-20% survivors have moderate-severe disability.
- Depends on stage at laser + post-laser complications.
MC twin scanning protocol UK
- Dating + chorionicity 11-13+6 wk.
- Detailed scans every 2 weeks from 16 weeks.
- Anomaly scan 20 weeks.
- Growth + Doppler ongoing.
- If TTTS / sFGR / TAPS: weekly+ scans.
Other MC complications
- sFGR: selective fetal growth restriction (~10-25% MC twins).
- TAPS: chronic blood imbalance without classic TTTS fluid changes.
- Discordant anomaly.
- MCMA twins: single sac, cord entanglement risk.
- Acardiac twin.
Different scenarios
Scenario 1: 20-wk MC twins, severe AFI discrepancy, Stage II
Fetal medicine referral within 24-48h. Laser surgery within days. Intensive monitoring.
Scenario 2: Stage I TTTS, watching
Weekly scans. Intervention if progresses.
Scenario 3: Stage IV with hydrops 26 weeks
Emergency laser. Steroids + magnesium. Delivery planning very preterm.
Scenario 4: Post-laser 28 weeks, twins stable
Continued surveillance. Plan delivery 34-36 wk if all well.
Scenario 5: One twin lost despite intervention
Surviving twin monitored intensely. Co-twin demise carries 10-30% surviving twin disability risk. Counselling + support.
Care guidance — MC twins / TTTS
- Confirm chorionicity 11-13 wk — crucial for scanning protocol.
- Every-2-week scans from 16 wk for MC twins.
- Specialist fetal medicine care.
- Early laser improves outcomes.
- Steroids if preterm delivery anticipated.
- Twins Trust (TAMBA) UK family support.
- NICU prepared for both twins.
- Long-term developmental follow-up.
Sources
- Quintero RA, et al. Staging of twin-twin transfusion syndrome. J Perinatol 1999.
- RCOG Green-top Guideline 51. Management of monochorionic twin pregnancy.
- NICE NG137. Twin and triplet pregnancy.
- Twins Trust (TAMBA). twinstrust.org.
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Frequently asked questions
What is twin-twin transfusion syndrome (TTTS)?
PREGNANCY COMPLICATION in identical twins sharing a SINGLE PLACENTA (monochorionic-diamniotic twins). Blood vessels in the placenta connect the twins; sometimes blood flow becomes UNEQUAL — one twin (DONOR) loses blood + becomes anaemic + dehydrated + has low amniotic fluid; the other (RECIPIENT) gets too much + develops polyhydramnios + heart strain + sometimes hydrops. AFFECTS ~10-15% of monochorionic twins. EMERGENCY without treatment — high mortality.
How is TTTS diagnosed?
ULTRASOUND surveillance of MC twins from 16 weeks. KEY SIGNS: (1) MAJOR AMNIOTIC FLUID discrepancy — DONOR's pocket <2 cm OR RECIPIENT >8 cm; (2) BLADDER VISIBILITY — donor's bladder not visible; recipient's distended; (3) DOPPLER changes; (4) GROWTH DISCREPANCY between twins. ALL MC TWINS need every-2-week scans from 16 weeks to detect early. EARLY DETECTION (Stage I) allows intervention before serious progression.
What's the Quintero staging?
Classification of TTTS SEVERITY 1-5. STAGE I: oligo/polyhydramnios but BOTH BLADDERS VISIBLE + Doppler normal. STAGE II: donor's BLADDER NOT VISIBLE. STAGE III: ABNORMAL DOPPLERS (umbilical artery, ductus venosus, umbilical vein). STAGE IV: HYDROPS (fluid in body cavities, severe heart failure) in one or both twins. STAGE V: ONE OR BOTH TWINS DEAD. PROGRESSION can be rapid; staging guides intervention.
What's the treatment?
(1) STAGE I: sometimes observation + close monitoring; some centres intervene; trial outcomes vary. (2) STAGES II-IV: FETOSCOPIC LASER COAGULATION first-line — minimally invasive procedure using a tiny telescope through mum's abdomen; lasers placental blood vessel connections between twins, separating circulations. SURVIVAL: ~85% at least one twin; ~70% both twins. (3) AMNIOREDUCTION (drainage of excess fluid from recipient): SOMETIMES if laser not available; less effective; bridge to laser. (4) DELIVERY: planned 32-36 weeks usually after laser; earlier if complications.
How is laser surgery done?
FETOSCOPIC LASER ABLATION (FLA). MOTHER under spinal/local anaesthetic; lying flat. SMALL incision in abdomen; FETOSCOPE (tiny telescope with camera) inserted into recipient's amniotic sac. PLACENTAL surface inspected for vessel connections (ANASTOMOSES). EACH connection between donor + recipient circulations LASERED — sealed shut. PROCEDURE 30-60 min usually. SOMETIMES amnioreduction at end (drain excess fluid). RECOVERY: usually next day discharge; bed rest 1-2 weeks; close ultrasound follow-up.
What are risks of laser surgery?
(1) MISCARRIAGE / preterm labour: ~5-10% within 7 days; (2) PPROM (waters break early): ~10-30%; (3) PLACENTAL ABRUPTION: rare; (4) BLEEDING; (5) INFECTION; (6) TARS (Twin Anaemia Polycythaemia Sequence) — different complication, ~5% post-laser; (7) RECURRENT TTTS — ~5%. RISKS BALANCED against UNTREATED TTTS mortality (~80-100% Stage III-IV). UK FETAL MEDICINE specialist centres only (e.g. Great Ormond Street, King's, UCL).
Where can I get TTTS treated in UK?
FETAL MEDICINE specialist centres: (1) GUY'S + ST THOMAS' / KING'S COLLEGE (London); (2) UCL (London); (3) UNIVERSITY HOSPITAL BIRMINGHAM; (4) ROYAL VICTORIA INFIRMARY (Newcastle); (5) ST MARY'S (Manchester); (6) other tertiary centres. REFERRAL from local obstetrician once TTTS suspected. SAME-WEEK assessment usual. TRANSFER for procedure. RECOVERY usually local follow-up.
What's the prognosis?
WITH LASER: at least one twin survives in ~85%; BOTH twins in ~70%. NEURODEVELOPMENTAL: ~10-20% of survivors have moderate-severe disability (cerebral palsy, learning disability) — depends on stage at laser + post-laser complications. WITHOUT TREATMENT: Stage II = ~80% mortality; Stage III-IV = nearly 100% mortality. EARLIER intervention better. POST-DELIVERY follow-up: developmental, cardiac, neurology for survivors.
Will I have a normal pregnancy after laser?
MONITORED CLOSELY but usually NO further intervention needed. ROUTINE: weekly ultrasounds for several weeks then biweekly; growth scans; Doppler studies; CTG. PRETERM BIRTH common (median ~32-34 weeks); planned delivery 32-36 weeks usually depending on outcomes. CAESAREAN often chosen but vaginal birth possible if twin 1 cephalic + stable. ANTENATAL STEROIDS if delivery <34 weeks.
Are there other monochorionic twin complications?
(1) SELECTIVE FETAL GROWTH RESTRICTION (sFGR) — one twin not growing; ~10-25% of MC twins; staged differently (Quintero or Gratacos); /calculators/sfgr-staging; (2) TWIN ANAEMIA POLYCYTHAEMIA SEQUENCE (TAPS) — chronic blood imbalance without classic TTTS fluid changes; ~5% spontaneous, ~5% post-laser; (3) DISCORDANT FETAL ANOMALY; (4) MONOCHORIONIC-MONOAMNIOTIC TWINS (single sac) — cord entanglement risk; (5) ACARDIAC TWIN. ALL need specialist fetal medicine care.
How often will I be scanned?
MC TWINS protocol UK: (1) DATING + chorionicity at 11-13+6 weeks; (2) NUCHAL TRANSLUCENCY 11-13+6 wk; (3) DETAILED SCANS every 2 WEEKS from 16 weeks (some from 14 wk); (4) ANOMALY scan ~20 weeks; (5) GROWTH + DOPPLER ongoing; (6) IF TTTS / sFGR / TAPS — weekly or more. INTENSE surveillance because complications can develop rapidly. SPECIALIST fetal medicine team co-care with obstetrics.
Will my babies need NICU?
OFTEN YES. PRETERM BIRTH common (median ~32-34 wk after laser). NICU admissions: respiratory support; growth concerns; transition support. POST-LASER complications (anaemia, polycythaemia) sometimes need transfusion / exchange. NEUROLOGY assessment + MRI for survivors. PARENTING two preterm twins demanding — BLISS / TAMBA (Twins Trust) support invaluable.
Can monochorionic twins be born by vaginal birth?
POSSIBLE in selected cases: (1) Twin 1 cephalic; (2) No TTTS/sFGR complications; (3) Adequate growth both twins; (4) Specialist obstetric team experienced. C-SECTION often chosen because: increased complication rate during second twin's delivery; mother's preference; concurrent indications. DISCUSSED with consultant. INDIVIDUALISED.
How does this relate to other calculators on BumpBites?
Companion: /calculators/sfgr-staging; /calculators/twin-probability; /calculators/cervical-length; /calculators/antenatal-steroids; /calculators/magnesium-sulphate; /calculators/biophysical-profile; /calculators/afi-sdp; /calculators/mca-psv.