RESUMEN
Congenital diaphragmatic hernia is a rare structural defect, usually diagnosed in the second or third trimester of pregnancy. We present here a case of left-sided diaphragmatic hernia diagnosed at 12 weeks of gestation and a short review of published reports on first trimester diagnosis of this defect. Ultrasound diagnosis of congenital diaphragmatic hernia cases, with early herniation of the viscera in the thorax, is feasible during the first trimester. The prerequisite is the systematic examination of the fetal anatomy. Hallmarks of the diagnosis, in the first trimester as well as later in pregnancy, are the presence of the stomach, bowel or liver in the chest, and the shift of the mediastinum. Early diagnosis of this defect is essential. This will allow timely intervention and appropriate management, following extensive parental counseling.