Edited sentence: If the uterus was kept relaxed and the utero-placental blood flow kept intact, the foetus could remain on a maternal 'heart-lung machine' while the airway was secured.In a select group of foetuses with CDH, tracheal occlusion is used to obstruct the normal flow of foetal lung fluid and to stimulate lung expansion and growth.The ex utero intrapartum treatment (EXIT) procedure was originally developed to reverse temporary tracheal occlusion in patients who had undergone foetal surgery for severe congenital diaphragmatic hernia (CDH).The solution was to arrange delivery in such a way that the occlusion could be removed and the airway secured while the baby remained on placental support.While the technique of tracheal occlusion remains under study in clinical trials, EXIT procedures have been shown to be useful for management of other causes of foetal airway obstruction.With the airway obstructed, airway management at birth is critical