Abstract
Congenital diaphragmatic hernia (CDH) is a severe developmental anomaly with variable clinical outcomes, influenced by factors such as liver herniation, pulmonary hypertension, and associated anomalies. While familial clustering of CDH has been described, its occurrence in monozygotic twins remains rare. We report the case of premature monozygotic female twins diagnosed prenatally with left-sided CDH, delivered at 30 weeks and 1 day of gestation due to maternal hemolysis, elevated liver enzyme levels, and low platelet levels (HELLP) syndrome. Both infants required immediate intubation and surgical correction. Twin A had no liver herniation or pulmonary hypertension and was discharged on day 66 with a relatively uncomplicated course, despite an episode of ileus that resolved conservatively. In contrast, Twin B presented with liver herniation, persistent pulmonary hypertension of the newborn (PPHN), and a hemodynamically significant patent ductus arteriosus (PDA). Despite PDA ligation, pulmonary pressures remained elevated, and cardiac catheterization revealed left pulmonary artery stenosis. Twin B also experienced reherniation of abdominal organs, necessitating a second diaphragmatic repair, and was discharged after 224 days with home oxygen therapy. This report illustrates the divergent clinical trajectories of genetically identical infants with CDH and highlights liver herniation, PPHN, and vascular anomalies as key prognostic factors. It underscores the importance of early prenatal diagnosis, individualized perinatal management, and the potential need for genetic evaluation in twin CDH cases.

Key words: Congenital diaphragmatic hernia, Monozygotic twins, Prematurity, Pulmonary hypertension, Liver herniation, Neonatal surgery.