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.