Cardiotocography only versus cardiotocography plus PR-interval analysis in intrapartum surveillance: a randomised, multicentre trial

Abstract

There is a need to improve the sensitivity and specificity of fetal monitoring during labour. We compared the gold standard, cardiotocography, with cardiotocography plus time-interval analysis of the fetal electrocardiogram in fetal surveillance. The aim was to find out whether time-interval analysis decreased the need for operative intervention due to fetal distress. We did a randomised, prospective trial in five hospitals in the UK, Hong Kong, the Netherlands, and Singapore. 1038 women undergoing high-risk labours were randomly assigned fetal monitoring by cardiotocography alone, or cardiotocography plus fetal electrocardiography (ECG). Outcomes measured were rates of operative intervention, and neonatal outcome. Analysis was by intention to treat. 515 women were assigned management by cardiotocography, and 523 cardiotocography plus fetal ECG. There was a trend towards fewer operative interventions for presumed fetal distress in the time-interval analysis plus cardiotocography group (63 [13%] vs 78 [16%]), but this was not significant (relative risk 0.80 [95% CI 0.59-1.08], p=0.17). There was no significant difference between groups in the proportion of babies who had an umbilical arterial pH of 7.15 or less (51 [11%] vs 49 [11%]; 1.01 [0.7-1.47]), or in the frequency of unsuspected acidaemia (42 [9%] vs 35 [8%]; 1.17 [0.76-1.79]). The addition of time-interval analysis of the fetal electrocardiogram during labour did not show a significant benefit in decreasing operative intervention. There was no significant difference in neonatal outcome.