In the Scandinavian congress of physiologists in 1959, Dr John Lind showed a film titled “Roentgen cinematographic studies on aeration of the lung at birth” (1). He demonstrated that tying the umbilical cord prior to the first breath reduces the size of the heart during the first three or four cardiac cycles. The heart again increased in size, almost to that of the fetal heart. This change in heart size was interpreted as the filling of the opened pulmonary vasculature occurring with onset of lung aeration after birth.

“If the umbilical circulation is closed, the flow from the caudal caval vein through via sinistra (umbilical venous stream flowing into the left atrium through the foramen ovale, as opposed to via dextra – flowing into the right ventricle) to the left heart will hardly suffice and for a moment the left heart will not have enough blood. On the basis of these observations, it would seem that the closing of the umbilical circulation before the aeration of the lungs has taken place is a highly ‘unphysiological’ measure, which should thus be avoided” (2).

“If the umbilical circulation is closed, the flow from the caudal caval vein through via sinistra (umbilical venous stream flowing into the left atrium through the foramen ovale, as opposed to via dextra – flowing into the right ventricle) to the left heart will hardly suffice and for a moment the left heart will not have enough blood. On the basis of these observations, it would seem that the closing of the umbilical circulation before the aeration of the lungs has taken place is a highly ‘unphysiological’ measure, which should thus be avoided” (2).

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