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ORPHA:95431

Twin to twin transfusion syndrome

low confidenceDisorder

Also known as: Feto-fetal transfusion syndrome

Publications

4,207

Trials

12

Interventional, condition-specific

Researchers

1,008

Distinct authors in sample

Gene link

—

Readiness

2/6

Stages with a signal

Clinical definition (Orphanet)

Twin twin transfusion syndrome (TTTS) is a rare condition seen in twin monochorionic pregnancies, typically developing during the 15-26 week gestation period and usually due to unbalanced intertwin placental anastomoses, where an unequal exchange of blood between twins causes oligohydramnios in one sac and polyhydramnios in the other which can lead to a high perinatal mortality rate and a high rate of disability in survivors if left untreated

Orphanet entry

Cross-references

Joined from Mondo / Orphanet. MeSH labels may enter searches; UMLS / OMIM / NCIT are stored for reference.

Additional Mondo synonyms (7)

Twin Anemia Polycythemia Sequence · Twin-Twin transfusion syndrome · foetal blood loss from foetal haemorrhage into co-twin · foetal haemorrhage into co-twin · placental transfusion syndrome · stuck Twin syndrome · twin-to-twin transfusion syndrome

Research stages

Trial readiness signals

Where this condition sits on an open-data research pipeline — not how close a treatment is, and not medical advice. Empty stages often mean “not in these databases under this Mondo ID,” not “impossible.”

2/6 stages with a signal

An interventional trial matched this condition name on ClinicalTrials.gov — see trials below.

  1. Gene identifiedNot found

    No GenCC disease–gene assertion in this build

  2. LiteraturePresent

    4,207 matched papers (2,223 in last 10 years) Source

  3. Phenotype characterisedNot found

    No HPO disease–phenotype associations via Monarch for these Mondo IDs

  4. Animal modelNot found

    No Alliance genotype “model of” associations via Monarch for these Mondo IDs

  5. Orphan designationNot found

    No FDA or EMA orphan-drug designation matched this disease via UMLS or preferred name Source

  6. Interventional trialPresent

    12 matched on ClinicalTrials.gov (5 recruiting in sample)

Biology

Genes and phenotypes

Gene–disease validity from GenCC, plus phenotypes and animal models joined from Monarch Initiative via Mondo ID — not a clinical diagnosis aid.

Do we know what causes it?

Not yet — the cause hasn't been pinned down in GenCC.

No strong gene–disease assertion joined for this Orphanet entity.

Phenotypes (Monarch / HPO)

None returned for this Mondo ID. That often means “not linked under this ID,” not “no clinical features.”

Animal models (Monarch / Alliance)

None returned for this Mondo ID. Empty here is not proof that no model organism work exists under another name or gene.

Monarch fetch 2026-07-29

Therapies

Designations, candidates, and chemicals

FDA OOPD and EMA orphan designations, Open Targets clinical candidates, and CTD chemical associations via MyDisease.info. These never change the interventional-trial headline.

Orphan designation (FDA · EMA)

No designation matched this disease via UMLS or preferred name on the FDA OOPD mirror or EMA orphan register. Absence here is not proof that none exists under another wording.

Open Targets candidates

No drugs or clinical candidates returned for this Mondo ID on Open Targets.

CTD chemicals (MyDisease.info)

No CTD chemical associations returned for this Mondo ID.

Literature

Is anyone studying this?

4,207

4,207 papers have been published on this condition. That is a real research literature — still far smaller than common diseases (breast cancer: over 700,000 papers). Median papers in the last 10 years for a rare disease in this dataset (publications denominator n=3967) is 59.

4,207 papers since the earliest indexed year in this search — median last-10-year count for a rare disease in this dataset is 59 (publications denominator n=3967).

2,223 in the last 10 years · low confidence

Phrase hits: 4,204 · MeSH hits: 17

Open Europe PMC search

Who's working on it?

1,008

Distinct author names in 200 sampled papers — named people below.

Who's working on it?

People publishing on this condition (sampled Europe PMC records). Affiliation is the most recent found in that sample.

  1. 01
    Khalil A15 papers · 2026

    Fetal Medicine Unit, Saint George's Hospital, University of London, London, United Kingdom.

    Papers in Europe PMC
  2. 02
    Slaghekke F12 papers · 2026

    Department of Obstetrics, Division of Fetal Therapy, Leiden University Medical Center, Leiden, the Netherlands.

    Papers in Europe PMC
  3. 03
    Lopriore E11 papers · 2026

    Department of Pediatrics, Division of Neonatology, Willem-Alexander Children's Hospital, Leiden University Medical Center, Leiden, the Netherlands.

    Papers in Europe PMC
  4. 04
    D'Antonio F8 papers · 2026

    Center for Fetal Care and High-Risk Pregnancy, University of Chieti, Chieti, Italy (D'Antonio).

    Papers in Europe PMC
  5. 05
    de Vries LS7 papers · 2026

    Department of Neonatology, University Medical Center Utrecht, Utrecht, the Netherlands.

    Papers in Europe PMC
  6. 06
    Mustafa HJ7 papers · 2026

    Division of Maternal-Fetal Medicine, Department of Obstetrics, Gynecology and Reproductive Sciences, University of Maryland School of Medicine, Baltimore, Maryland, USA.

    Papers in Europe PMC
  7. 07
    Tollenaar LSA7 papers · 2026

    Department of Obstetrics, Division of Fetal Therapy, Leiden University Medical Center, Leiden, the Netherlands.

    Papers in Europe PMC
  8. 08
    Baschat AA6 papers · 2026

    Johns Hopkins Center for Fetal Therapy, Department of Gynecology and Obstetrics, Johns Hopkins University School of Medicine, Baltimore, MD, USA.

    Papers in Europe PMC
  9. 09
    Belfort MA6 papers · 2026

    Department of Obstetrics and Gynecology, Baylor College of Medicine and Texas Children's Hospital, Houston, TX, USA.

    Papers in Europe PMC
  10. 10
    Espinoza J6 papers · 2026

    Division of Fetal Intervention, Department of Obstetrics, Gynecology and Reproductive Sciences, McGovern Medical School, University of Texas Health Science Center, Houston, TX, USA.

    Papers in Europe PMC

Clinical research

Is a treatment being tested?

12

interventional trials for this specific condition

12 interventional trials matched this specific condition name; 5 currently recruiting in our sample.

Data as of 11 September 2026

12 interventional trials — more than 77.2% of diseases in the trials denominator have none at all (5501 of 7126; this disease is at the 93.2th percentile).

low confidence · 93.2th percentile (trials denominator)

Recruiting interventional trials

From the matched ClinicalTrials.gov set

12 interventional trials matched after quoted-phrase search and title/condition post-filter.

Observational and natural-history studies

12 observational studies match this condition. These do not test a treatment and are not counted in the interventional-trial headline, but they are genuine research: natural-history work often defines the endpoints needed for a future rare-disease trial, and families may be able to enroll.

Recruiting or not-yet-recruiting

Open the complete matched search on ClinicalTrials.gov

Other registries (secondary)

Broader net from EU CTIS, ISRCTN, and ICTRP when available — deduped against ClinicalTrials.gov IDs already counted above. Dual-model LLM relevance gates what we keep. These rows are not added to the interventional headline.

raw 10 · after dedupe 10 · already on CT.gov 0 · kept 0 · parent 0 · uncertain 10 · dropped 0 · fetched 2026-07-30

Source notes: ictrp: Error: ICTRP public search unavailable (WHO portal is SPA-only; SOAP needs partnership). Tried: https://apps.who.int/tri

No secondary-registry studies passed dual-model relevance for this condition name (after dedupe).

Uncertain / not reviewed (10)

Where to find support

Condition-specific patient organisations, when Orphanet lists them, are on the disease’s Orphanet page. We also link umbrella groups that support undiagnosed and ultra-rare families.

Orphanet entry for Twin to twin transfusion syndrome — check Associations / patient organisations on that page.

India — NPRD

Last verified 2026-07-26

This ORPHAcode is not on our curated NPRD list (direct or Mondo-parent match). That does not decide clinical eligibility; families in India should ask a notified Centre of Excellence about current coverage.

Hand-curated for this project. ORPHAcode mappings are best-effort and may be incomplete or imprecise for umbrella categories. Parent (Mondo) matches mean the policy lists a broader category — confirm eligibility with a Centre of Excellence. Financial entitlements summarised from public policy statements and may change. This is not official government guidance.

How we counted this

Europe PMC query (preferred label + any corrected label + Orphanet and Mondo exact synonyms, stoplisted; unioned with resolved MeSH labels when available). UMLS / OMIM / NCIT cross-references are stored on the overview but are not added to the query string.

"Twin to twin transfusion syndrome" OR "Feto-fetal transfusion syndrome" OR "Twin Anemia Polycythemia Sequence" OR "Twin-Twin transfusion syndrome" OR "foetal blood loss from foetal haemorrhage into co-twin" OR "foetal haemorrhage into co-twin" OR "placental transfusion syndrome" OR "stuck Twin syndrome" OR "twin-to-twin transfusion syndrome"

Run this search on Europe PMC

MeSH descriptor terms unioned into the query: Fetofetal Transfusion

ClinicalTrials.gov query (quoted phrases + MeSH via query.cond, plus recall-expansion terms when used):

"Twin to twin transfusion syndrome" OR "Feto-fetal transfusion syndrome" OR "Twin Anemia Polycythemia Sequence" OR "Twin-Twin transfusion syndrome" OR "foetal blood loss from foetal haemorrhage into co-twin" OR "foetal haemorrhage into co-twin" OR "placental transfusion syndrome" OR "stuck Twin syndrome" OR "twin-to-twin transfusion syndrome" OR "Fetofetal Transfusion"

Interventional trials matched via: phrase, mesh (mesh = registered under a MeSH descriptor no name phrase would catch; recall-expansion = gene / selected parent terms used only for trials).

Study-type breakdown: 12 interventional · 12 observational · 0 expanded access. Only interventional studies enter the trial headline.

Query health: ok — strategies attempted: phrase, mesh; with hits: phrase, mesh

Run this search on ClinicalTrials.gov

Confidence reasoning

  • Preferred label is multi-word and distinctive
  • No synonyms dropped by stoplist
  • No label/synonym collisions with other diseases in this corpus
  • Publication count (4207) is extremely high with unknown/missing prevalence — treat as possible over-matching, not proven research intensity

Ingested 2026-07-27T04:42:44.179Z