Although thoraco-amniotic shunting (TAS) for severe pleural effusion is an effective fetal treatment, there are some cases in which it deteriorates, showing circulatory collapse. To evaluate the usefulness of umbilical venous blood flow volume (UVFV) for predicting deterioration, we analyzed the fetal low UVFV situation.

In 22 cases of fetal severe pleural effusion, we measured UVFV/fetal estimated birth weight (mL/minute/kg) prospectively before and after TAS by ultrasonography. We defined low UVFV/kg as < 50 mL/minute/kg (2.5 percentile) and compared subgroups based on their UVFV value and analyzed the outcome after birth.

Total survival rate was 59% at 6 months. Seven cases in the low group before delivery (UVFV/kg 19.5) showed poor prognoses, such as fetal/neonatal death and longer neonatal intensive care unit management (100% vs. the normal UVFV group 40%, p = 0.017). The low group also showed umbilical artery absent end-diastolic velocity (71%); edema resolved in 50%, suggesting hypo inflow from the placenta and fetal hypocardiac output status, revealing fetal cardiac collapse.

UVFV analyses would be a new marker of fetal management of severe pleural effusion, suggesting low UVFV after TAS seems to be hypovolemic cardiac collapse and shows poor prognosis, and we had better consider immediate delivery to prevent death even after TAS.

The data that support the findings of this study are available from the corresponding author (Y.T.) upon reasonable request.

Received: 28 June 2025

Accepted: 13 August 2025

Accepted Manuscript online:
08 September 2025

Article published online:
16 September 2025

© 2025. The Author(s). This is an open access article published by Thieme under the terms of the Creative Commons Attribution 4.0 International License, permitting copying and reproduction so long as the original work is given appropriate credit (https://creativecommons.org/licenses/by/4.0/)

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