The intraventricular conduction time of fetal heart in pregnancies complicated by rhesus haemolytic disease.

The duration and shape of the fetal QRS complex were studied in 88 pregnancies complicated by rhesus isoimmunization. A clear correlation between ventricular depolarization time and haemoglobin levels at birth was observed. A single QRS value greater than 4 SD above the normal mean value, or a tendency to rapid increase was very suggestive of a bad prognosis, while a QRS duration below +4 SD or declining in sequential determinations reflects a temporary compensation of fetal conditions. From the QRS complex analysis a clear indication appeared of the constant and early involvement of the heart in terms of myocardial hypertrophy and/or cardiac enlargement. The sensitivity of QRS to anaemia and the feasibility of continuous non-invasive monitoring might allow, with the determination of bilirubin concentration in amniotic fluid, improvement in the management of rhesus haemolytic disease.