Changes in cardiac morphometry in fetuses with lower urinary tract obstruction

Abstract Objective Fetal lower urinary tract obstruction (LUTO) is associated with significant perinatal morbidity due to oligohydramnios, pulmonary hypoplasia, and progressive renal dysfunction. In addition to these well‐known sequelae, LUTO has been linked to various cardiac abnormalities on prenatal imaging, including cardiomegaly; ventricular hypertrophy; pericardial effusion; and, in some cases, relatively small left‐sided cardiac structures. This study aimed to comprehensively characterize detailed fetal echocardiographic features in LUTO and compare them with gestational age (GA)‐matched controls, adjusting for estimated fetal weight (EFW), with an emphasis on quantitative cardiac dimensions. Methods This retrospective cohort study included fetuses diagnosed with isolated LUTO who underwent at least one fetal echocardiogram at our institution from 2013 to 2025. Fetuses with known genetic abnormalities or additional major structural anomalies were excluded. Controls consisted of GA‐matched (1:1) fetuses with normal cardiac anatomy. Quantitative cardiac measurements were compared between groups and adjusted for EFW. Results Among 117 LUTO fetuses who underwent at least one fetal echocardiogram, qualitative findings included pericardial effusion (29%), right ventricular hypertrophy (27%), and left ventricular hypertrophy (25%). Compared with controls, LUTO fetuses demonstrated significantly higher cardiothoracic ratio and smaller cardiac structures, including the mitral and tricuspid valves, aortic and pulmonary valves, and branch pulmonary arteries (all p < 0.01). These differences remained significant after adjustment for EFW. Conclusion Fetuses with LUTO demonstrate global cardiac morphometric changes, affecting both the left‐ and right‐sided structures. These may reflect impaired diastolic filling or decreased venous return. Our findings highlight the potential value of serial fetal echocardiography particularly following fetal intervention for monitoring cardiac adaptation and informing perinatal counseling.