The non-stress test is the most commonly used method in prepartal surveillance. Due to the high intra- and interobserver variability involved in subjective evaluation, the computer-assisted analysis is gaining in importance. Some studies have shown that low foetal STV may be associated with higher rates of acidosis and intrauterine mortality. Other factors influencing STV are largely not known. Low STV has been found as an effect of cortisone. In this case report, we illustrate the relevance of haemodilation therapy in the context of essential hypertension in the 27 (th) week of gestation and its effect on SVT. The treatment led to a prolongation of pregnancy to the 32 (nd) week. At the start of treatment STV increased to 4.5 ms and dropped back below this value concurrently with centralisation as documented by Doppler sonography. STV correlated clearly with the foetal condition. However, STV is dependent on numerous factors which should be investigated in further studies in order to determine appropriate reference values.