Supplementary Material for: Fetoscopic endoluminal tracheal occlusion in congenital diaphragmatic hernia: Unraveling the impact of prematurity and suboptimal fetal lung growth

Introduction
Congenital diaphragmatic hernia (CDH) poses significant challenges in both prenatal diagnosis and postnatal management. Fetoscopic endoluminal tracheal occlusion (FETO) aims to enhance survival rates among patients with severe CDH, defined by an observed-to-expected lung-to-head ratio (o/e LHR) of less than 25%. However, issues such as preterm delivery and suboptimal fetal lung growth (SFLG) complicate outcomes. This study examines the effects of these critical risks on FETO results.

Methods
Data were retrospectively gathered from the multi-institutional CDH Study Group registry on patients with CDH who underwent FETO between 2015 and 2023. Key metrics included CDHSG stage, gestational age (with preterm defined as <37 weeks), o/e-LHR, FETO details, and survival outcomes. The primary outcome was survival, correlated with lung growth and prematurity.

Results
Among 4,524 CDH patients, 106 (2.3%) received FETO, however, 43 patients had o/e-LHR data. Analyses revealed an overall survival rate of 72.1%, though survival for patients delivered preterm with SFLG decreased to 57.1%, while survival among term patients with any increase in fetal lung growth was 90.0%. In univariate analyses, the balloon inflation duration (p=0.05), the use of extracorporeal life support (p=0.04), and the post-balloon o/e LHR (p=0.04) were associated with survival, while in a multivariable logistic regression, the change in o/e-LHR after FETO (OR=1.07, p=0.05) was the only variable found to be significantly associated with survival.

Conclusion
Prematurity and SFLG are critical factors linked to decreased survival in FETO, with improved o/e-LHR correlating with better outcomes. Future research should focus on refining patient selection and procedural protocols, with a particular focus on mitigating known complications such as preterm delivery and SFLG, to enhance survival rates.