ORPHA:617297
Twin-reversed arterial perfusion sequence
Also known as: TRAP
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.
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=183) is 38.
323 papers since the earliest indexed year in this search — median last-10-year count for a rare disease in this dataset is 38 (publications denominator n=183).
178 in the last 10 years · medium confidence · 79th percentile (publications denominator)
Is a treatment being tested?
1
trials for this specific condition
1 interventional trial matched this specific condition name; 1 currently recruiting in our sample.
Data as of 26 July 2026
1 interventional trial — more than 59.2% of diseases in the trials denominator have none at all (151 of 255; this disease is at the 65.3th percentile).
medium confidence · 65.3th percentile (trials denominator)
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.
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
Recruiting interventional trials
Trials testing a treatment from the matched ClinicalTrials.gov set
1 interventional trials matched after quoted-phrase search and title/condition post-filter.
Where to find support
We do not yet link condition-specific patient organisations. These umbrella groups support undiagnosed and ultra-rare families:
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 below 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.
Cross-references (from Mondo): UMLS:C5575500
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