Intrapartum fetal monitoring by ST-analysis of the fetal ECG

Abstract

Objective Intrapartum fetal monitoring aims to identify fetuses at risk for neonatal and long-term injury due to asphyxia. To serve this purpose, cardiotocography (CTG) combined with ST-analysis of the fetal electrocardiogram (ECG), which is a relatively new method, may be used. The main aim of this thesis was to quantify the (cost) effectiveness of intrapartum fetal monitoring by ST-analysis of the fetal ECG in women with a singleton term pregnancy in cephalic position. Methods Several studies were performed to answer the research questions addressed in this thesis. The main study was a multicentre randomised clinical trial among labouring women, who were randomly assigned to monitoring by CTG combined with ST-analysis of the fetal ECG (index group) or CTG without ST-analysis of the fetal ECG (control group). There were strict conditions for performance of fetal blood sampling (FBS). Primary outcome was metabolic acidosis defined as umbilical cord-artery pH below 7.05 combined with a base deficit calculated in the extracellular fluid compartment above 12 mmol/L. Secondary outcomes were metabolic acidosis calculated in blood, number of low Apgar scores, total neonatal admissions, admissions to Neonatal Intensive Care Unit (NICU), number of newborns with moderate to severe hypoxic ischemic encephalopathy (HIE), operative deliveries, number of cases with FBS and costs. The analysis was performed according to intention-to-treat. Secondary analyses of the trial data were performed regarding all cases with adverse neonatal outcome and deliveries monitored by ST-analysis in which FBS had been performed. Results From January 2006 to July 2008, 5667 women were randomised in the clinical trial. 2827 women were assigned to the index and 2840 to the control group. The FBS rate was 10.6% in the index group versus 20.4% in the control group (RR 0.52; 95% CI 0.46 to 0.60). The incidence of the primary outcome was 0.7% in the index group versus 1.1% in the control group (RR 0.70; 95% CI 0.38 to 1.28). When metabolic acidosis was calculated in blood, these rates were 1.6% and 2.6%, respectively (RR 0.63; 95% CI 0.42 to 0.94). The number of operative deliveries, low Apgar scores, neonatal admissions and newborns with moderate or severe HIE was comparable in both groups. Per delivery, the mean costs per patient of CTG plus ST-analysis were €29 (95% CI: - € 9 to € 77) higher than of CTG only. The incremental costs of CTG plus ST-analysis to prevent one case of metabolic acidosis (primary outcome) were €7.250 and the number needed to treat (NNT) 250. Secondary analyses showed that monitoring by ST-analysis of the fetal ECG is more specific and comprehensive, regarding the aim to detect and deliver compromised fetuses, than monitoring by CTG only. Consequent adherence to the STAN clinical guidelines may further decrease the necessity for FBS in addition to ST-analysis of the fetal ECG. Conclusions Intrapartum fetal monitoring by ST-analysis of the fetal ECG appears to be a cost-effective, less-invasive en more specific strategy than monitoring by CTG only.