The Significance of the Changes in the Continuous Fetal Heart Rate in the First Stage of Labour

Summary A comparison between data derived from changes in fetal heart rate and p H of fetal blood in 279 high‐risk patients is described. The incidence of fetal acidosis was low when the continuous record of FHR showed good beat‐to‐beat variation in rhythm and no slowing during uterine contractions. The incidence of fetal acidosis accompanying fetal tachycardia or bradycardia was low if the rate remained unaltered during contractions. Decelerations of fetal heart rate accompanied by baseline tachycardia and/or loss of beat‐to‐beat variation were the changes most commonly associated with fetal acidosis and hence, by inference, with fetal asphyxia. Deep and/or delayed decelerations were also suggestive of fetal asphyxia. Late decelerations, although at first sight innocuous, were frequently found to be a sign of severe fetal asphyxia.