Relationship between intra-thoracic and -amniotic pressures and the impact of amnioreduction on thoraco-amniotic shunting efficacy: Insights from a case series.

Objective: To report on a series of 12 cases of fetal pleural effusion (FPE), focusing on the relationship between intra-thoracic pressure (ITP) and intra-amniotic pressure (IAP) and its impact on the efficacy of thoraco-amniotic shunting (TAS). Methods: This single-center case series study included patients with FPE undergoing TAS or amnioreduction (AR). ITP and IAP were measured before and after the initial thoracocentesis and AR. Results: TAS was performed 21 times, and AR was performed 7 times. The median gestational age at thoracocentesis was 28 weeks and 2 days (18 wk 1 d-33 wk 2 d). The median FPE volume normalized to the estimated fetal weight was 30 (15 -81) mL/kg. The median pre-thoracocentesis ITP was 15 (12 -28) mmHg, and the post-thoracocentesis ITP was 10 (5 -19) mmHg. In four patients with hydrops, TAS alone did not improve hydrops. However, hydrops improved after AR in three of these patients. In these cases, the IAP decreased following AR. The post-AR IAP was higher than the post-thoracocentesis ITP in the patients whose hydrops did not improve, whereas the post-AR IAP was lower than or equal to the post-thoracocentesis ITP in the patients whose hydrops improved. Conclusion: FPE reduction and hydrops improvement after TAS may require the IAP to be lower than the ITP.