Effect of right- vs left-sided congenital diaphragmatic hernia and duration of tracheal occlusion on longitudinal lung-size changes.

objectivesTo describe patterns of lung-size changes after fetoscopic endoluminal tracheal occlusion (FETO) in cases of right-sided congenital diaphragmatic hernia (RCDH) compared with in cases of left-sided congenital diaphragmatic hernia (LCDH), and the association between lung growth and the duration of occlusion.

methodsThis was a longitudinal observational cohort study conducted at three fetal surgery centers (UZ Leuven, Leuven, Belgium; BCNatal, Barcelona, Spain; The Heart Hospital of São Paulo, São Paulo, Brazil) using similar prenatal management protocols. Inclusion criteria were pregnant women with a fetus with isolated congenital diaphragmatic hernia (CDH) that underwent FETO between July 2002 and October 2021 with a minimum of two measurements of the fetal observed-to-expected lung-to-head ratio (o/e-LHR) (one before and at least one after FETO) available. The o/e-LHR was used as a proxy for fetal lung size. Other variables were the side of the defect and gestational age at FETO and at balloon removal. Multilevel analysis was used to model longitudinal changes in fetal lung size. The changes in o/e-LHR during the occlusion period (∆ o/e-LHR (%), referred to as 'change in absolute lung size') were calculated and corrected for baseline measurement ('proportional' lung size change (%)) and expressed as a function of the duration of occlusion (referred to as proportional lung growth rate (%/day)). A structural break point was used to identify a significant change in proportional lung growth rate during the occlusion period. Patterns of proportional lung-size change and proportional lung growth rate were compared between RCDH and LCDH using Student's t-test.

resultsWe reported 1026 o/e-LHR measurements in 338 fetuses (RCDH, n = 73; LCDH, n = 265). The pattern of lung growth after FETO was comparable in cases of RCDH and LCDH, with a sharp increase in size immediately after occlusion (60% vs 50%, respectively, compared with baseline measurements), followed by a slower increase over the remainder of the observation period. Overall, over the 6-week period, lung size in cases of RCDH expanded by 140% compared with baseline, while in cases of LCDH lung size expanded by 100% (P < 0.001). The pattern of proportional lung growth rate was also similar, starting with a high growth rate at day 2 after FETO, followed by slower but persistent growth. In cases of RCDH, lungs had a slower initial growth rate compared with LCDH (13.11%/day (95% CI, 3.72-22.52%/day) vs 15.67%/day (95% CI, 6.69-24.66%/day); P < 0.001). The proportional growth rates over the 6-week period were comparable between RCDH and LCDH (2.91%/day vs 1.84%/day; P = 0.081). The structural break point showed a significant change in growth rate at day 5 and day 31 after FETO for cases of LCDH and day 8 after FETO for cases of RCDH.

conclusionThere are measurable differences in proportional lung growth rates after FETO between cases of RCDH and LCDH. However, the pattern of lung-size changes parallel each other, with an initial fast growth rate that dropped to a lower but persisting rate later in the occlusion period. The continued increase in fetal lung size observed after FETO supports previous observations that the duration of occlusion may influence the treatment response in CDH. © 2026 International Society of Ultrasound in Obstetrics and Gynecology.