Twin Reversed Arterial Perfusion (TRAP) Sequence: Proposal for Morphologic Classification System Predicting Natural History.

OBJECTIVE

To establish a new classification system for Twin Reversed Arterial Perfusion (TRAP) sequence based on specific skeletal morphological characteristics, and to evaluate its prognostic relevance in expectantly managed.

METHODS

Single center retrospective cohort study of TRAP sequence cases between February 2001 and April 2022 that were expectantly managed. Cases were classified into five morphological types: Type I (Hemiacardius), Type II (Acardius Holosomus), Type III (Acephalus Trunk), Type IV (Acephalus Acormus), and Type V (Acardius Amorphous). Pump twin outcomes for prognosis were compared among the five types.

RESULTS

Of 116 cases expectantly managed, the most common type was type III (41.4%), followed by type II (23.3%), type I (17.2%), type IV (7.8%), and type V (10.3%). Among these 116 cases, 29 (25.0%) had favorable outcomes, whereas 87 (75.0%) had an adverse outcome. Survival rates differed significantly by type (p = 0.001): Type V, 66.7% (8/12); Type IV, 33.3% (3/9); Type II, 22.2% (6/27); Type III, 18.8% (9/48); and Type I, 15.0% (3/20).

CONCLUSIONS

In this series of expectantly managed TRAP-cases, pump twin survival was highest when the acardiac twin exhibited minimal structural development. Early sonographic classification may support prenatal counseling in the TRAP sequence.