A congenital diaphragmatic hernia may result from failure of the

B. The formation of the diaphragm occurs through the fusion of tissue from four different sources. The pleuroperitoneal membranes normally fuse with the three other components during week 6 of development. Abnormal development or fusion of one or both of the pleuroperitoneal membranes causes a patent opening between the thorax and abdomen through which abdominal viscera may herniate.