Thoracoabdominal Cysts in the First Trimester as an Early Sonographic Sign of Congenital Diaphragmatic Hernia: A Case Series.

First-trimester fetal abdominal cysts at the right thoracoabdominal border are typically regarded as benign findings. We report three cases in which such cysts, initially attributed to hepatic or pulmonary origin, subsequently evolved into right-sided congenital diaphragmatic hernia (CDH), providing additional sonographic evidence for a previously under-recognized pattern. Notably, cyst regression in the second trimester coincided with-rather than preceded-the development of intrathoracic hepatic herniation. Recognition of this pattern may facilitate earlier CDH diagnosis and improve perinatal counseling.