Fetal plasma catecholamine concentrations and fetal heart-rate variability during first stage of labour.

Fetal heart-rate (FHR) variability was studied in 50 term fetuses during the first stage of labour. The variability was computed as an arbitrary index during a 20-min period preceding a fetal scalp blood sample which was used for the measurement of pH, adrenaline and noradrenaline. None of the fetuses was found to have a scalp blood pH less than 7.2. The short-term variability index was significantly correlated with the noradrenaline concentration in fetal blood, but the adrenaline levels which were generally very low showed no correlation with the variability values. There was no correlation between variability index and cervical dilatation or blood pH. We have shown previously high plasma catecholamine concentrations in the asphyxiated fetus with a decreased pH. In this study where fetal pH was normal a correlation between FHR variability and fetal scalp plasma noradrenaline levels was found. Thus an increased FHR variability might be an early sign of fetal distress when fetal pH is still normal.