The authors describe a case of fetal sinusoidal cardiac rhythm which was observed during a feto-maternal transfusion. This type of cardiographic tracing is found similarly in certain cases of severe fetal anaemia or of isolated fetal hypoxia. It is also found in amnionitis and associated with various iatrogenic factors such as the administration of general anaesthesia and fetoscopy. The literature does not show a consensus when trying to find the criteria for defining this type of rhythm. The aetiology of the pathological condition is much in dispute. The prognosis does not have to be all that serious. In conclusion, the authors suggest the attitude of management to lessen the poor prognosis of these sinusoidal rhythms and help towards a favourable outcome.