A congenital disorder, in which failure of proper development of the DIAPHRAGM leads to herniation into the chest cavity of intra-abdominal organs such as the stomach, small intestine and/or liver. The fetal lung cannot develop properly as a result. It is usually diagnosed antenatally on routine ultraound screening, with arrangements then made for the baby to be delivered in a specialist centre where neonatal surgery can be performed, since without such a facility the baby is likely to have major breathing problems so may be difficult to resuscitate at birth. In a few cases and in fetal medicine centres, it may be possible and necessary to perform surgery on the affected fetus by FETOSCOPY.