The value of the short‐term fetal heart rate variation for timing the delivery of growth‐retarded fetuses

Objective To assess the clinical value of the short‐term fetal heart rate variation (STV) for timing the delivery of severely growth‐retarded fetuses, many associated with pre‐eclampsia. Design Retrospective cohort study. Setting John Radcliffe Maternity Hospital, Oxford, UK. Population Two hundred and fifty‐seven fetuses with a birthweight less than third percentile and a last computerised cardiotocography performed within 24 h of delivery. Methods Analysis of the relationship between antepartum STV and the perinatal outcome. Main outcome measures Stillbirth rate and the acid–base status at birth. Results There were no stillbirths or neonatal deaths (NNDs) within 24 h in the study population. Decreasing STV was correlated with earlier deliveries (P < 0.001), lower birthweight (P < 0.001), lower umbilical artery pH at birth (P < 0.001), worse acid–base status at birth (P < 0.001) and worse postnatal outcome (P < 0.002). The STV was able to predict the presence or absence of acidaemia and metabolic acidaemia (area under the receiver operating characteristic curve 0.70 and 0.75, respectively, P < 0.001). The risk of metabolic acidaemia increased as the antepartum STV decreased, the optimum cutoff level being ≤ 3.0 milliseconds (positive and negative predictive values 64.6 and 86.6%). An STV ≤ 3.0 milliseconds was associated with markedly higher rate of metabolic acidaemia and early NNDs compared with an STV > 3.0 milliseconds (54.2 versus 10.5% and 8.3 versus 0.5%, respectively; P < 0.001). The deaths of the former group were all due to extreme prematurity and very low birthweight. Conclusions The antepartum STV is an important marker of perinatal outcome in severely growth‐retarded fetuses. Timing the delivery of the most preterm and small fetuses remains a difficult task.