ORPHA:617297
Twin-reversed arterial perfusion sequence
Also known as: TRAP
Publications
323
66.2th percentile
Trials
1
Interventional, condition-specific
Researchers
928
Distinct authors in sample
Gene link
—
Readiness
2/6
Stages with a signal
Clinical definition (Orphanet)
A rare disorder related to monochorionic twin pregnancy characterized by complete or partial absence of cardiac development in one twin (''acardiac twin'') and blood supply of both circulations by the morphologically normal co-twin (''pump twin'') via an arterioarterial anastomosis. In most cases, the acardiac twin has well developed legs and pelvis but no cephalic pole, thoracic organs, and upper extremities. The condition is associated with a high risk of perinatal death of the pump twin due to a combination of high-output cardiac failure and polyhydramnios-related pre-term birth. Hypoxia and intrauterine growth restriction are also seen in the pump twin.
How rare: How common this is has not been clearly measured.
Cross-references
Joined from Mondo / Orphanet. MeSH labels may enter searches; UMLS / OMIM / NCIT are stored for reference.
- MONDO:0850014
- UMLS:C5575500
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.
- Gene identifiedNot found
No GenCC disease–gene assertion in this build
- LiteraturePresent
323 matched papers (178 in last 10 years) Source
- Phenotype characterisedNot found
No HPO disease–phenotype associations via Monarch for these Mondo IDs
- Animal modelNot found
No Alliance genotype “model of” associations via Monarch for these Mondo IDs
- Orphan designationNot found
No FDA or EMA orphan-drug designation matched this disease via UMLS or preferred name Source
- Interventional trialPresent
1 matched on ClinicalTrials.gov (1 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 2026-07-27
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?
323
323 papers have ever been published on this condition (under this name). For scale, breast cancer has over 700,000. Median papers in the last 10 years for a rare disease in this dataset (publications denominator n=3967) is 59.
323 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).
178 in the last 10 years · medium confidence · 66.2th percentile (publications denominator)
Phrase hits: 323 · MeSH hits: 0
Who's working on it?
928
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.
- 01Li X9 papers · 2026
Obstetrics and Gynecology Hospital, Fudan University, Shanghai, China.
Papers in Europe PMC - 02Geipel A6 papers · 2026
Department of Obstetrics and Prenatal Medicine, University Hospital Bonn, Bonn, Germany.
Papers in Europe PMC - 03Zhou Q6 papers · 2025
Obstetrics and Gynecology Hospital, Fudan University, Shanghai, China.
Papers in Europe PMC - 04Gembruch U5 papers · 2026
Division of Fetal Surgery, Department of Obstetrics and Prenatal Medicine, University of Bonn, Bonn, Germany.
Papers in Europe PMC - 05Khalil A5 papers · 2026
Fetal Medicine Unit, St George's University of London, London, UK. Electronic address: akhalil@sgul.ac.uk.
Papers in Europe PMC - 06Li L5 papers · 2024
Department of Obstetrics and Gynecology, Peking University Third Hospital, Beijing, China.
Papers in Europe PMC - 07Li S5 papers · 2025
Department of Obstetrics and Gynecology, Peking University Third Hospital, Beijing, China.
Papers in Europe PMC - 08Strizek B5 papers · 2026
Department of Obstetrics and Prenatal Medicine, University Hospital Bonn, Bonn, Germany.
Papers in Europe PMC - 09Wang J5 papers · 2022
Department of MRI, Shandong Medical Imaging Research Institute, Jinan 250021, China.
Papers in Europe PMC - 10Zhao Y5 papers · 2025
Obstetrics and Gynecology Hospital, Fudan University, Shanghai, China.
Papers in Europe PMC
Clinical research
Is a treatment being tested?
1
interventional trials for this specific condition
1 interventional trial matched this specific condition name; 1 currently recruiting in our sample.
Data as of 9 September 2026
1 interventional trial — more than 77.2% of diseases in the trials denominator have none at all (5501 of 7126; this disease is at the 80.1th percentile).
medium confidence · 80.1th percentile (trials denominator)
Recruiting interventional trials
From the matched ClinicalTrials.gov set
1 interventional trials matched after quoted-phrase search and title/condition post-filter.
- NCT02621645·RECRUITING·TRAP Intervention STudy: Early Versus Late Intervention for Twin Reversed Arterial Perfusion Sequence
Uncertain·Conditions: Twin Reversal Arterial Perfusion Syndrome·Matched via name phraseAt least one provider returned uncertain or parent-category.
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 1 · after dedupe 1 · already on CT.gov 0 · kept 0 · parent 0 · uncertain 1 · dropped 0 · fetched 2026-07-27
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 (1)
- isrctn·ISRCTN16879394·No longer recruiting·FERN: Intervention or expectant management for early onset selective fetal growth restriction in monochorionic twin pregnancy
Uncertain — At least one provider returned uncertain or parent-category.
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-reversed arterial perfusion sequence — check Associations / patient organisations on that page.
India — NPRD
Last verified 2026-07-26This 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-reversed arterial perfusion sequence"
ClinicalTrials.gov query (quoted phrases + MeSH via query.cond, plus recall-expansion terms when used):
"Twin-reversed arterial perfusion sequence"
Interventional trials matched via: phrase (mesh = registered under a MeSH descriptor no name phrase would catch; recall-expansion = gene / selected parent terms used only for trials).
Study-type breakdown: 1 interventional · 0 observational · 0 expanded access. Only interventional studies enter the trial headline.
Query health: ok — strategies attempted: phrase; with hits: phrase
Run this search on ClinicalTrials.gov
Synonyms dropped by stoplist: TRAP
Confidence reasoning
- Preferred label is multi-word and distinctive
- 1 synonym(s) dropped by stoplist (may under-count)
- No label/synonym collisions with other diseases in this corpus
Ingested 2026-07-26T01:37:44.187Z