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New research · Obstetrics & Gynecology
Ultrasound in obstetrics & gynecology : the official journal of the International Society of Ultrasound in Obstetrics and Gynecology · 1d
Cohort studyUltrasound in obstetrics & gynecology : the official journal of the International Society of Ultrasound in Obstetrics and Gynecology · 2026

Development and external validation of prognostic markers to predict pump-twin survival in twin reversed arterial perfusion sequence.

L-H Wu, Y-Y Yang, H Shen … H-N Xie
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Obstetrics & GynecologyCohort study

A twin weight ratio below 0.295 is associated with better pump-twin survival.

Development and external validation of prognostic markers to predict pump-twin survival in twin reversed arterial perfusion sequence.

L-H Wu et al. · Ultrasound in obstetrics & gynecology : the official journal of the International Society of Ultrasound in Obstetrics and Gynecology · 2026
Purpose

To evaluate the outcome of monochorionic diamniotic (MCDA) pregnancies complicated by twin reversed arterial perfusion (TRAP) sequence and to evaluate potential prognostic ultrasound markers as predictors of pump-twin survival.

Methods

This was a retrospective cohort study of MCDA twin pregnancies diagnosed with TRAP sequence at two medical centers in China between January 2010 and December 2024.

n = 117 MCDA pregnancies
Results

below this weight ratio of the malformed to healthy twin, survival is better

AUC 0.86 (95% CI 0.73 to 0.99)
null = 00.730.99
CI excludes the null - significant
More results

The overall pump-twin survival rate was 65.8% (77/117).

Three variables (URL and URL/CRL ratio in the first trimester and TWR in the second trimester) were identified to be independent risk factors influencing pump-twin survival in both the primary and external-validation cohorts.

More results

The TWR exhibited good calibration, but URL and the URL/CRL ratio exhibited poor calibration.

However, the optimal cut-offs of URL and the URL/CRL ratio showed no statistical difference in the external-validation cohort.

“
Conclusion · 1 of 3

After 14 + 0 weeks' gestation, the threshold of TWR < 0.295 can reliably predict survival of the pump twin in MCDA pregnancies with TRAP sequence.

Conclusion · 2 of 3

However, the predictive value of URL and the URL/CRL ratio in the first trimester for pump-twin survival is poor.

Conclusion · 3 of 3

A well-designed prospective multicenter study is warranted to develop a first-trimester multivariable predictive model with enhanced predictive performance. © 2026 International Society of Ultrasound in Obstetrics and Gynecology.

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